[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added inline comments.



Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:119
+  if (!SwitchHasDefault && SwitchCaseCount == 0) {
+diag(Switch->getLocStart(), "degenerated switch without labels");
+return;

aaron.ballman wrote:
> JonasToth wrote:
> > aaron.ballman wrote:
> > > I think a better way to phrase this one is: "switch statement without 
> > > labels has no effect" and perhaps have a fix-it to replace the entire 
> > > switch construct with its predicate?
> > The fixit would only aim for the sideeffects the predicate has, right? I 
> > would consider such a switch as a bug or are there reasonable things to 
> > accomplish? Given its most likely unintended code i dont think a fixit is 
> > good.
> > 
> > Fixing the code removes the warning and might introduce a bug.
> This code pattern comes up with machine-generated code with some frequency, 
> so I was thinking it would be nice to automatically fix that code. However, I 
> think you're right that "fixing" the code may introduce bugs because you 
> don't want to keep around non-side effecting operations and that's 
> complicated. e.g.,
> ```
> switch (i) { // Don't replace this with i;
> }
> 
> switch (some_function_call()) { // Maybe replace this with 
> some_function_call()?
> }
> 
> switch (i = 12) { // Should definitely be replaced with i = 12;
> }
> ```
> Perhaps only diagnosing is the best option.
I will add another FIXME. The if-is-better pattern might be reasonable 
transformable and doing this allows addressing the issue again later.


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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth updated this revision to Diff 139304.
JonasToth marked 3 inline comments as done.
JonasToth added a comment.

- add fixme for degenerated switch


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737

Files:
  clang-tidy/hicpp/CMakeLists.txt
  clang-tidy/hicpp/HICPPTidyModule.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
  docs/ReleaseNotes.rst
  docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/hicpp-multiway-paths-covered-else.cpp
  test/clang-tidy/hicpp-multiway-paths-covered.cpp

Index: test/clang-tidy/hicpp-multiway-paths-covered.cpp
===
--- /dev/null
+++ test/clang-tidy/hicpp-multiway-paths-covered.cpp
@@ -0,0 +1,468 @@
+// RUN: %check_clang_tidy %s hicpp-multiway-paths-covered %t
+
+enum OS { Mac,
+  Windows,
+  Linux };
+
+struct Bitfields {
+  unsigned UInt : 3;
+  int SInt : 1;
+};
+
+int return_integer() { return 42; }
+
+void bad_switch(int i) {
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // No default in this switch
+  switch (i) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+break;
+  case 1:
+break;
+  case 2:
+break;
+  }
+
+  // degenerate, maybe even warning
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch statement without labels has no effect
+  }
+
+  switch (int j = return_integer()) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+break;
+  }
+
+  // Degenerated, only default case.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // Degenerated, only one case label and default case -> Better as if-stmt.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch could be better written as an if/else statement
+  case 0:
+break;
+  default:
+break;
+  }
+
+  unsigned long long BigNumber = 0;
+  switch (BigNumber) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  const int &IntRef = i;
+  switch (IntRef) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  char C = 'A';
+  switch (C) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 'A':
+break;
+  case 'B':
+break;
+  }
+
+  Bitfields Bf;
+  // UInt has 3 bits size.
+  switch (Bf.UInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.UInt) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+break;
+  }
+  // SInt has 1 bit size, so this is somewhat degenerated.
+  switch (Bf.SInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.SInt) {
+  case 0:
+  case 1:
+break;
+  }
+
+  bool Flag = false;
+  switch (Flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case true:
+break;
+  }
+
+  switch (Flag) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // This `switch` will create a frontend warning from '-Wswitch-bool' but is
+  // ok for this check.
+  switch (Flag) {
+  case true:
+break;
+  case false:
+break;
+  }
+}
+
+void unproblematic_switch(unsigned char c) {
+  //
+  switch (c) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+  case 8:
+  case 9:
+  case 10:
+  case 11:
+  case 12:
+  case 13:
+  case 14:
+  case 15:
+  case 16:
+  case 17:
+  case 18:
+  case 19:
+  case 20:
+  case 21:
+  case 22:
+  case 23:
+  case 24:
+  case 25:
+  case 26:
+  case 27:
+  case 28:
+  case 29:
+  case 30:
+  case 31:
+  case 32:
+  case 33:
+  case 34:
+  case 35:
+  case 36:
+  case 37:
+  case 38:
+  case 39:
+  case 40:
+  case 41:
+  case 42:
+  case 43:
+  case 44:
+  case 45:
+  case 46:
+  case 47:
+  case 48:
+  case 49:
+  case 50:
+  case 51:
+  case 52:
+  case 53:
+  case 54:
+  case 55:
+  case 56:
+  case 57:
+  case 58:
+  case 59:
+  case 60:
+  case 61:
+  case 62:
+  case 63:
+  case 64:
+  case 65:
+  case 66:
+  case 67:
+  case 68:
+  case 69:
+  case 70:
+  case 71:
+  case 72:
+  case 73:
+  case 74:
+  case 75:
+  case 76:
+  case 77:
+  case 78:
+  case 79:
+  case 80:
+  case 81:
+

[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman accepted this revision.
aaron.ballman added a comment.
This revision is now accepted and ready to land.

LGTM!




Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:119
+  if (!SwitchHasDefault && SwitchCaseCount == 0) {
+diag(Switch->getLocStart(), "degenerated switch without labels");
+return;

JonasToth wrote:
> aaron.ballman wrote:
> > I think a better way to phrase this one is: "switch statement without 
> > labels has no effect" and perhaps have a fix-it to replace the entire 
> > switch construct with its predicate?
> The fixit would only aim for the sideeffects the predicate has, right? I 
> would consider such a switch as a bug or are there reasonable things to 
> accomplish? Given its most likely unintended code i dont think a fixit is 
> good.
> 
> Fixing the code removes the warning and might introduce a bug.
This code pattern comes up with machine-generated code with some frequency, so 
I was thinking it would be nice to automatically fix that code. However, I 
think you're right that "fixing" the code may introduce bugs because you don't 
want to keep around non-side effecting operations and that's complicated. e.g.,
```
switch (i) { // Don't replace this with i;
}

switch (some_function_call()) { // Maybe replace this with some_function_call()?
}

switch (i = 12) { // Should definitely be replaced with i = 12;
}
```
Perhaps only diagnosing is the best option.


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737



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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added inline comments.



Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:119
+  if (!SwitchHasDefault && SwitchCaseCount == 0) {
+diag(Switch->getLocStart(), "degenerated switch without labels");
+return;

aaron.ballman wrote:
> I think a better way to phrase this one is: "switch statement without labels 
> has no effect" and perhaps have a fix-it to replace the entire switch 
> construct with its predicate?
The fixit would only aim for the sideeffects the predicate has, right? I would 
consider such a switch as a bug or are there reasonable things to accomplish? 
Given its most likely unintended code i dont think a fixit is good.

Fixing the code removes the warning and might introduce a bug.


Repository:
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https://reviews.llvm.org/D40737



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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth updated this revision to Diff 139293.
JonasToth marked 4 inline comments as done.
JonasToth added a comment.

- adress review comments


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737

Files:
  clang-tidy/hicpp/CMakeLists.txt
  clang-tidy/hicpp/HICPPTidyModule.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
  docs/ReleaseNotes.rst
  docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/hicpp-multiway-paths-covered-else.cpp
  test/clang-tidy/hicpp-multiway-paths-covered.cpp

Index: test/clang-tidy/hicpp-multiway-paths-covered.cpp
===
--- /dev/null
+++ test/clang-tidy/hicpp-multiway-paths-covered.cpp
@@ -0,0 +1,468 @@
+// RUN: %check_clang_tidy %s hicpp-multiway-paths-covered %t
+
+enum OS { Mac,
+  Windows,
+  Linux };
+
+struct Bitfields {
+  unsigned UInt : 3;
+  int SInt : 1;
+};
+
+int return_integer() { return 42; }
+
+void bad_switch(int i) {
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // No default in this switch
+  switch (i) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+break;
+  case 1:
+break;
+  case 2:
+break;
+  }
+
+  // degenerate, maybe even warning
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch statement without labels has no effect
+  }
+
+  switch (int j = return_integer()) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+break;
+  }
+
+  // Degenerated, only default case.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // Degenerated, only one case label and default case -> Better as if-stmt.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch could be better written as an if/else statement
+  case 0:
+break;
+  default:
+break;
+  }
+
+  unsigned long long BigNumber = 0;
+  switch (BigNumber) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  const int &IntRef = i;
+  switch (IntRef) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  char C = 'A';
+  switch (C) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 'A':
+break;
+  case 'B':
+break;
+  }
+
+  Bitfields Bf;
+  // UInt has 3 bits size.
+  switch (Bf.UInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.UInt) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+break;
+  }
+  // SInt has 1 bit size, so this is somewhat degenerated.
+  switch (Bf.SInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.SInt) {
+  case 0:
+  case 1:
+break;
+  }
+
+  bool Flag = false;
+  switch (Flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case true:
+break;
+  }
+
+  switch (Flag) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // This `switch` will create a frontend warning from '-Wswitch-bool' but is
+  // ok for this check.
+  switch (Flag) {
+  case true:
+break;
+  case false:
+break;
+  }
+}
+
+void unproblematic_switch(unsigned char c) {
+  //
+  switch (c) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+  case 8:
+  case 9:
+  case 10:
+  case 11:
+  case 12:
+  case 13:
+  case 14:
+  case 15:
+  case 16:
+  case 17:
+  case 18:
+  case 19:
+  case 20:
+  case 21:
+  case 22:
+  case 23:
+  case 24:
+  case 25:
+  case 26:
+  case 27:
+  case 28:
+  case 29:
+  case 30:
+  case 31:
+  case 32:
+  case 33:
+  case 34:
+  case 35:
+  case 36:
+  case 37:
+  case 38:
+  case 39:
+  case 40:
+  case 41:
+  case 42:
+  case 43:
+  case 44:
+  case 45:
+  case 46:
+  case 47:
+  case 48:
+  case 49:
+  case 50:
+  case 51:
+  case 52:
+  case 53:
+  case 54:
+  case 55:
+  case 56:
+  case 57:
+  case 58:
+  case 59:
+  case 60:
+  case 61:
+  case 62:
+  case 63:
+  case 64:
+  case 65:
+  case 66:
+  case 67:
+  case 68:
+  case 69:
+  case 70:
+  case 71:
+  case 72:
+  case 73:
+  case 74:
+  case 75:
+  case 76:
+  case 77:
+  case 78:
+  case 79:
+  case 80:
+  case 81:
+  case 82:

[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.



Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:68
+}
+/// This function calculate 2 ** Bits and returns
+/// numeric_limits::max() if an overflow occured.

Add some vertical whitespace before the comments.



Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:75
+}
+/// Get the number of possible values that can be switched on for the type T.
+///

Same here.



Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:79
+/// - numeric_limits::max() when overflow appeared due to
+///   more then 64 bits type size.
+static std::size_t getNumberOfPossibleValues(QualType T,

s/then/than



Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:119
+  if (!SwitchHasDefault && SwitchCaseCount == 0) {
+diag(Switch->getLocStart(), "degenerated switch without labels");
+return;

I think a better way to phrase this one is: "switch statement without labels 
has no effect" and perhaps have a fix-it to replace the entire switch construct 
with its predicate?



Comment at: docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst:95
+
+  Activates warning for missing``else`` branches. Default is `0`.

Missing whitespace after "missing". May want to clarify that that this is a 
Boolean option.


Repository:
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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth updated this revision to Diff 138851.
JonasToth added a comment.

- remove spurious debug iostream


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737

Files:
  clang-tidy/hicpp/CMakeLists.txt
  clang-tidy/hicpp/HICPPTidyModule.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
  docs/ReleaseNotes.rst
  docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/hicpp-multiway-paths-covered-else.cpp
  test/clang-tidy/hicpp-multiway-paths-covered.cpp

Index: test/clang-tidy/hicpp-multiway-paths-covered.cpp
===
--- /dev/null
+++ test/clang-tidy/hicpp-multiway-paths-covered.cpp
@@ -0,0 +1,468 @@
+// RUN: %check_clang_tidy %s hicpp-multiway-paths-covered %t
+
+enum OS { Mac,
+  Windows,
+  Linux };
+
+struct Bitfields {
+  unsigned UInt : 3;
+  int SInt : 1;
+};
+
+int return_integer() { return 42; }
+
+void bad_switch(int i) {
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // No default in this switch
+  switch (i) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+break;
+  case 1:
+break;
+  case 2:
+break;
+  }
+
+  // degenerate, maybe even warning
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch without labels
+  }
+
+  switch (int j = return_integer()) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+break;
+  }
+
+  // Degenerated, only default case.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // Degenerated, only one case label and default case -> Better as if-stmt.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch could be better written as an if/else statement
+  case 0:
+break;
+  default:
+break;
+  }
+
+  unsigned long long BigNumber = 0;
+  switch (BigNumber) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  const int &IntRef = i;
+  switch (IntRef) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  char C = 'A';
+  switch (C) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 'A':
+break;
+  case 'B':
+break;
+  }
+
+  Bitfields Bf;
+  // UInt has 3 bits size.
+  switch (Bf.UInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.UInt) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+break;
+  }
+  // SInt has 1 bit size, so this is somewhat degenerated.
+  switch (Bf.SInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.SInt) {
+  case 0:
+  case 1:
+break;
+  }
+
+  bool Flag = false;
+  switch (Flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case true:
+break;
+  }
+
+  switch (Flag) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // This `switch` will create a frontend warning from '-Wswitch-bool' but is
+  // ok for this check.
+  switch (Flag) {
+  case true:
+break;
+  case false:
+break;
+  }
+}
+
+void unproblematic_switch(unsigned char c) {
+  //
+  switch (c) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+  case 8:
+  case 9:
+  case 10:
+  case 11:
+  case 12:
+  case 13:
+  case 14:
+  case 15:
+  case 16:
+  case 17:
+  case 18:
+  case 19:
+  case 20:
+  case 21:
+  case 22:
+  case 23:
+  case 24:
+  case 25:
+  case 26:
+  case 27:
+  case 28:
+  case 29:
+  case 30:
+  case 31:
+  case 32:
+  case 33:
+  case 34:
+  case 35:
+  case 36:
+  case 37:
+  case 38:
+  case 39:
+  case 40:
+  case 41:
+  case 42:
+  case 43:
+  case 44:
+  case 45:
+  case 46:
+  case 47:
+  case 48:
+  case 49:
+  case 50:
+  case 51:
+  case 52:
+  case 53:
+  case 54:
+  case 55:
+  case 56:
+  case 57:
+  case 58:
+  case 59:
+  case 60:
+  case 61:
+  case 62:
+  case 63:
+  case 64:
+  case 65:
+  case 66:
+  case 67:
+  case 68:
+  case 69:
+  case 70:
+  case 71:
+  case 72:
+  case 73:
+  case 74:
+  case 75:
+  case 76:
+  case 77:
+  case 78:
+  case 79:
+  case 80:
+  case 81:
+  case 82:
+  case 83:
+  case 84:
+  case 85:
+  case 86:

[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added a comment.

I think the check is ready to land. I did check run it over LLVM and found some 
interesting code parts that could benefit. I extracted all the warnings and 
sorted them into the categories `missing default/covered 
codepath(uncovered.txt)`, `better use if/else(better_if.txt)` and `use 
if(mandatory_if.txt)`. Some warnings come from generated files but some live in 
usercode. In total there are 540 warnings.

Please note, that i identified a common pattern to leave out the `default` 
label and add an ending `llvm_unreachable` that is outside the switch but 
ensures there is no unwanted fall_through. Most of the warnings for the first 
category are like this, but i could not check all of them!

F5899267: uncovered.txt 

F5899266: better_if.txt 

F5899265: mandatory_if.txt 


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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth updated this revision to Diff 138850.
JonasToth added a comment.

- reorder check in release notes to get it in alphabetical order


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737

Files:
  clang-tidy/hicpp/CMakeLists.txt
  clang-tidy/hicpp/HICPPTidyModule.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
  docs/ReleaseNotes.rst
  docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/hicpp-multiway-paths-covered-else.cpp
  test/clang-tidy/hicpp-multiway-paths-covered.cpp

Index: test/clang-tidy/hicpp-multiway-paths-covered.cpp
===
--- /dev/null
+++ test/clang-tidy/hicpp-multiway-paths-covered.cpp
@@ -0,0 +1,468 @@
+// RUN: %check_clang_tidy %s hicpp-multiway-paths-covered %t
+
+enum OS { Mac,
+  Windows,
+  Linux };
+
+struct Bitfields {
+  unsigned UInt : 3;
+  int SInt : 1;
+};
+
+int return_integer() { return 42; }
+
+void bad_switch(int i) {
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // No default in this switch
+  switch (i) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+break;
+  case 1:
+break;
+  case 2:
+break;
+  }
+
+  // degenerate, maybe even warning
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch without labels
+  }
+
+  switch (int j = return_integer()) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+break;
+  }
+
+  // Degenerated, only default case.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // Degenerated, only one case label and default case -> Better as if-stmt.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch could be better written as an if/else statement
+  case 0:
+break;
+  default:
+break;
+  }
+
+  unsigned long long BigNumber = 0;
+  switch (BigNumber) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  const int &IntRef = i;
+  switch (IntRef) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  char C = 'A';
+  switch (C) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 'A':
+break;
+  case 'B':
+break;
+  }
+
+  Bitfields Bf;
+  // UInt has 3 bits size.
+  switch (Bf.UInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.UInt) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+break;
+  }
+  // SInt has 1 bit size, so this is somewhat degenerated.
+  switch (Bf.SInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.SInt) {
+  case 0:
+  case 1:
+break;
+  }
+
+  bool Flag = false;
+  switch (Flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case true:
+break;
+  }
+
+  switch (Flag) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // This `switch` will create a frontend warning from '-Wswitch-bool' but is
+  // ok for this check.
+  switch (Flag) {
+  case true:
+break;
+  case false:
+break;
+  }
+}
+
+void unproblematic_switch(unsigned char c) {
+  //
+  switch (c) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+  case 8:
+  case 9:
+  case 10:
+  case 11:
+  case 12:
+  case 13:
+  case 14:
+  case 15:
+  case 16:
+  case 17:
+  case 18:
+  case 19:
+  case 20:
+  case 21:
+  case 22:
+  case 23:
+  case 24:
+  case 25:
+  case 26:
+  case 27:
+  case 28:
+  case 29:
+  case 30:
+  case 31:
+  case 32:
+  case 33:
+  case 34:
+  case 35:
+  case 36:
+  case 37:
+  case 38:
+  case 39:
+  case 40:
+  case 41:
+  case 42:
+  case 43:
+  case 44:
+  case 45:
+  case 46:
+  case 47:
+  case 48:
+  case 49:
+  case 50:
+  case 51:
+  case 52:
+  case 53:
+  case 54:
+  case 55:
+  case 56:
+  case 57:
+  case 58:
+  case 59:
+  case 60:
+  case 61:
+  case 62:
+  case 63:
+  case 64:
+  case 65:
+  case 66:
+  case 67:
+  case 68:
+  case 69:
+  case 70:
+  case 71:
+  case 72:
+  case 73:
+  case 74:
+  case 75:
+  case 76:
+  case 77:
+  case 78:
+  case 79:
+  case 80:
+  case 81:
+  case 82:
+  case 83:
+  

[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth updated this revision to Diff 138849.
JonasToth added a comment.

- get the check working again
- enable the big test


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737

Files:
  clang-tidy/hicpp/CMakeLists.txt
  clang-tidy/hicpp/HICPPTidyModule.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
  docs/ReleaseNotes.rst
  docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/hicpp-multiway-paths-covered-else.cpp
  test/clang-tidy/hicpp-multiway-paths-covered.cpp

Index: test/clang-tidy/hicpp-multiway-paths-covered.cpp
===
--- /dev/null
+++ test/clang-tidy/hicpp-multiway-paths-covered.cpp
@@ -0,0 +1,468 @@
+// RUN: %check_clang_tidy %s hicpp-multiway-paths-covered %t
+
+enum OS { Mac,
+  Windows,
+  Linux };
+
+struct Bitfields {
+  unsigned UInt : 3;
+  int SInt : 1;
+};
+
+int return_integer() { return 42; }
+
+void bad_switch(int i) {
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // No default in this switch
+  switch (i) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+break;
+  case 1:
+break;
+  case 2:
+break;
+  }
+
+  // degenerate, maybe even warning
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch without labels
+  }
+
+  switch (int j = return_integer()) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+break;
+  }
+
+  // Degenerated, only default case.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // Degenerated, only one case label and default case -> Better as if-stmt.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch could be better written as an if/else statement
+  case 0:
+break;
+  default:
+break;
+  }
+
+  unsigned long long BigNumber = 0;
+  switch (BigNumber) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  const int &IntRef = i;
+  switch (IntRef) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  char C = 'A';
+  switch (C) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 'A':
+break;
+  case 'B':
+break;
+  }
+
+  Bitfields Bf;
+  // UInt has 3 bits size.
+  switch (Bf.UInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.UInt) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+break;
+  }
+  // SInt has 1 bit size, so this is somewhat degenerated.
+  switch (Bf.SInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.SInt) {
+  case 0:
+  case 1:
+break;
+  }
+
+  bool Flag = false;
+  switch (Flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case true:
+break;
+  }
+
+  switch (Flag) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // This `switch` will create a frontend warning from '-Wswitch-bool' but is
+  // ok for this check.
+  switch (Flag) {
+  case true:
+break;
+  case false:
+break;
+  }
+}
+
+void unproblematic_switch(unsigned char c) {
+  //
+  switch (c) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+  case 8:
+  case 9:
+  case 10:
+  case 11:
+  case 12:
+  case 13:
+  case 14:
+  case 15:
+  case 16:
+  case 17:
+  case 18:
+  case 19:
+  case 20:
+  case 21:
+  case 22:
+  case 23:
+  case 24:
+  case 25:
+  case 26:
+  case 27:
+  case 28:
+  case 29:
+  case 30:
+  case 31:
+  case 32:
+  case 33:
+  case 34:
+  case 35:
+  case 36:
+  case 37:
+  case 38:
+  case 39:
+  case 40:
+  case 41:
+  case 42:
+  case 43:
+  case 44:
+  case 45:
+  case 46:
+  case 47:
+  case 48:
+  case 49:
+  case 50:
+  case 51:
+  case 52:
+  case 53:
+  case 54:
+  case 55:
+  case 56:
+  case 57:
+  case 58:
+  case 59:
+  case 60:
+  case 61:
+  case 62:
+  case 63:
+  case 64:
+  case 65:
+  case 66:
+  case 67:
+  case 68:
+  case 69:
+  case 70:
+  case 71:
+  case 72:
+  case 73:
+  case 74:
+  case 75:
+  case 76:
+  case 77:
+  case 78:
+  case 79:
+  case 80:
+  case 81:
+  case 82:
+  case 83:
+  case 84:
+  c

[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added a subscriber: rsmith.
JonasToth added a comment.

Good news: The stack overflow seems to be fixed, by the patch r326624 from 
@rsmith (Thank you very much!).
Bad news: The check does not do its job anymore I try to fix the 
functionality problems.


Repository:
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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In https://reviews.llvm.org/D40737#1025777, @lebedev.ri wrote:

> In https://reviews.llvm.org/D40737#1024120, @JonasToth wrote:
>
> > After long inactivity (sorry!) i had a chance to look at it again:
> >
> >   switch(i) {
> >   case 0:;
> >   case 1:;
> >   case 2:;
> >   ...
> >   }
> >
> >
> > does *NOT* lead to the stack overflow. This is most likely an issue in the 
> > AST:
> >  https://godbolt.org/g/vZw2BD
> >
> > Empty case labels do nest, an empty statement prevents this. The nesting 
> > leads most likely to the deep recursion. I will file a bug for it.
>
>
> FWIW here are my 5 cent: this is a preexisting bug. Your testcase just 
> happened to expose it.
>  I'd file the bug, and then simply adjust the testcases here not to trigger 
> it and re-land this diff.
>
> I'm not sure what is to be gained by not doing that.
>  Of course, the bug is a bug, and should  be fixed, but it exists regardless 
> of this differential...


Just because a particular check triggers an issue elsewhere doesn't mean we 
should gloss over the issue in the check. That just kicks the can farther down 
the road so that our users find the issue. In this case, the check is likely to 
push users *towards* discovering that AST bug rather than away from it which is 
why I'm giving the push-back.


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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added a comment.

In https://reviews.llvm.org/D40737#1024120, @JonasToth wrote:

> After long inactivity (sorry!) i had a chance to look at it again:
>
>   switch(i) {
>   case 0:;
>   case 1:;
>   case 2:;
>   ...
>   }
>
>
> does *NOT* lead to the stack overflow. This is most likely an issue in the 
> AST:
>  https://godbolt.org/g/vZw2BD
>
> Empty case labels do nest, an empty statement prevents this. The nesting 
> leads most likely to the deep recursion. I will file a bug for it.


FWIW here are my 5 cent: this is a preexisting bug. Your testcase just happened 
to expose it.
I'd file the bug, and then simply adjust the testcases here not to trigger it 
and re-land this diff.

I'm not sure what is to be gained by not doing that.
Of course, the bug is a bug, and should  be fixed, but it exists regardless of 
this differential...


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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added a comment.

After long inactivity (sorry!) i had a chance to look at it again:

  switch(i) {
  case 0:;
  case 1:;
  case 2:;
  ...
  }

does *NOT* lead to the stack overflow. This is most likely an issue in the AST:
https://godbolt.org/g/vZw2BD

Empty case labels do nest, an empty statement prevents this. The nesting leads 
most likely to the deep recursion. I will file a bug for it.


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https://reviews.llvm.org/D40737



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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth updated this revision to Diff 129686.
JonasToth added a comment.

- get up to date to 7.0


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737

Files:
  clang-tidy/hicpp/CMakeLists.txt
  clang-tidy/hicpp/HICPPTidyModule.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
  docs/ReleaseNotes.rst
  docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/hicpp-multiway-paths-covered-else.cpp
  test/clang-tidy/hicpp-multiway-paths-covered.cpp

Index: test/clang-tidy/hicpp-multiway-paths-covered.cpp
===
--- /dev/null
+++ test/clang-tidy/hicpp-multiway-paths-covered.cpp
@@ -0,0 +1,472 @@
+// RUN: %check_clang_tidy %s hicpp-multiway-paths-covered %t
+
+enum OS { Mac,
+  Windows,
+  Linux };
+
+struct Bitfields {
+  unsigned UInt : 3;
+  int SInt : 1;
+};
+
+int return_integer() { return 42; }
+
+void bad_switch(int i) {
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // No default in this switch
+  switch (i) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+break;
+  case 1:
+break;
+  case 2:
+break;
+  }
+
+  // degenerate, maybe even warning
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch without labels
+  }
+
+  switch (int j = return_integer()) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+break;
+  }
+
+  // Degenerated, only default case.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // Degenerated, only one case label and default case -> Better as if-stmt.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch could be better written as an if/else statement
+  case 0:
+break;
+  default:
+break;
+  }
+
+  unsigned long long BigNumber = 0;
+  switch (BigNumber) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  const int &IntRef = i;
+  switch (IntRef) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  char C = 'A';
+  switch (C) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 'A':
+break;
+  case 'B':
+break;
+  }
+
+  Bitfields Bf;
+  // UInt has 3 bits size.
+  switch (Bf.UInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.UInt) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+break;
+  }
+  // SInt has 1 bit size, so this is somewhat degenerated.
+  switch (Bf.SInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.SInt) {
+  case 0:
+  case 1:
+break;
+  }
+
+  bool Flag = false;
+  switch (Flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case true:
+break;
+  }
+
+  switch (Flag) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // This `switch` will create a frontend warning from '-Wswitch-bool' but is
+  // ok for this check.
+  switch (Flag) {
+  case true:
+break;
+  case false:
+break;
+  }
+}
+
+void unproblematic_switch(unsigned char c) {
+  //
+  switch (c) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+  case 8:
+  case 9:
+  case 10:
+  case 11:
+  case 12:
+  case 13:
+  case 14:
+  case 15:
+  case 16:
+  case 17:
+  case 18:
+  case 19:
+  case 20:
+  case 21:
+  case 22:
+  case 23:
+  case 24:
+  case 25:
+  case 26:
+  case 27:
+  case 28:
+  case 29:
+  case 30:
+  case 31:
+  case 32:
+  case 33:
+  case 34:
+  case 35:
+  case 36:
+  case 37:
+  case 38:
+  case 39:
+  case 40:
+  case 41:
+  case 42:
+  case 43:
+  case 44:
+  case 45:
+  case 46:
+  case 47:
+  case 48:
+  case 49:
+  case 50:
+  case 51:
+  case 52:
+  case 53:
+  case 54:
+  case 55:
+  case 56:
+  case 57:
+  case 58:
+  case 59:
+  case 60:
+  case 61:
+  case 62:
+  case 63:
+  case 64:
+  case 65:
+  case 66:
+  case 67:
+  case 68:
+  case 69:
+  case 70:
+  case 71:
+  case 72:
+  case 73:
+  case 74:
+  case 75:
+  case 76:
+  case 77:
+  case 78:
+  ca

[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added a comment.

@sbenza and/or @klimek did you have time to address the stackoverflow caused 
from the ASTMatchers?

I forgot to add the link to the original break: 
http://green.lab.llvm.org/green/job/clang-stage2-cmake-RgSan/5470/consoleFull#17462642768254eaf0-7326-4999-85b0-388101f2d404


Repository:
  rCTE Clang Tools Extra

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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added a comment.

It does still regress! In a sense this is a WIP that i did not clarify.(which i 
do now)

While debugging the issue it seemed that parsing the AST did result in the 
stack overflow and not my check specific code.
Looping over all case Labels seems to be done in a recursive manner, which 
results in a massive stack (about 600 Frames or more while debugging). I am 
trying to better isolate the issue to be able to specify the problem more 
precise.

The odd thing to me was, that only the RelWithDebInfo build showed this 
behaviour. Building clang with MinSizeRel + Sanitizer did not show a stack 
overflow. I assume that the Debug Info increase the stack frame size. The 
release builds should overflow as well but with more case labels.

My goals for investigation:

- Figure out exactly which part of the matcher is the problem
- Rewrite the matchers and try to figure out a way to not use recursive 
functions to figure out the properties of the switch statement. Could 
information like `CaseCount` and `hasDefault` be interesting to have as member 
functions in the frontend? I think that can be added into Sema (i never touched 
anything there, so noo experience)
- Figure out when the Release Build will stackoverflow.

Would it be acceptable to allow a Stackoverflow when there are thousands of 
case labels? If i understand correctly (and AST-dump suggests it as well) each 
case label is another layer in the tree. If that is true other parts of clang 
might suffer from a similar issue.


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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

I would like to see the large test case added back in -- it was demonstrating a 
real problem with the code and it would be good to ensure we don't regress that 
behavior again in the future.


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[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Jonas Toth via Phabricator via cfe-commits]

JonasToth created this revision.
Herald added subscribers: cfe-commits, xazax.hun, mgorny.

The original check did break the green buildbot in the sanitizer build.
It took a while to redroduce and understand the issue.

There occured a stackoverflow while parsing the AST. The testcase with
256 case labels was the problem because each case label added another
stackframe. It seemed that the issue occured only in 'RelWithDebInfo' builds
and not in normal sanitizer builds.

To simplify the matchers the recognition for the different kinds of switch
statements has been moved into a seperate function and will not be done with
ASTMatchers. This is an attempt to reduce recursion and stacksize as well.

The new check removed this big testcase. Covering all possible values is still
implemented for bitfields and works there. The same logic on integer types
will lead to the issue.


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737

Files:
  clang-tidy/hicpp/CMakeLists.txt
  clang-tidy/hicpp/HICPPTidyModule.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
  clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
  docs/ReleaseNotes.rst
  docs/clang-tidy/checks/hicpp-multiway-paths-covered.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/hicpp-multiway-paths-covered-else.cpp
  test/clang-tidy/hicpp-multiway-paths-covered.cpp

Index: test/clang-tidy/hicpp-multiway-paths-covered.cpp
===
--- /dev/null
+++ test/clang-tidy/hicpp-multiway-paths-covered.cpp
@@ -0,0 +1,206 @@
+// RUN: %check_clang_tidy %s hicpp-multiway-paths-covered %t
+
+enum OS { Mac,
+  Windows,
+  Linux };
+
+struct Bitfields {
+  unsigned UInt : 3;
+  int SInt : 1;
+};
+
+int return_integer() { return 42; }
+
+void bad_switch(int i) {
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // No default in this switch
+  switch (i) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+break;
+  case 1:
+break;
+  case 2:
+break;
+  }
+
+  // degenerate, maybe even warning
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch without labels
+  }
+
+  switch (int j = return_integer()) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+  case 2:
+break;
+  }
+
+  // Degenerated, only default case.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // Degenerated, only one case label and default case -> Better as if-stmt.
+  switch (i) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch could be better written as an if/else statement
+  case 0:
+break;
+  default:
+break;
+  }
+
+  unsigned long long BigNumber = 0;
+  switch (BigNumber) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  const int &IntRef = i;
+  switch (IntRef) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+
+  char C = 'A';
+  switch (C) {
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 'A':
+break;
+  case 'B':
+break;
+  }
+
+  Bitfields Bf;
+  // UInt has 3 bits size.
+  switch (Bf.UInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: potential uncovered code path; add a default label
+  case 0:
+  case 1:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.UInt) {
+  case 0:
+  case 1:
+  case 2:
+  case 3:
+  case 4:
+  case 5:
+  case 6:
+  case 7:
+break;
+  }
+  // SInt has 1 bit size, so this is somewhat degenerated.
+  switch (Bf.SInt) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case 0:
+break;
+  }
+  // All paths explicitly covered.
+  switch (Bf.SInt) {
+  case 0:
+  case 1:
+break;
+  }
+
+  // Some paths are covered by the switch and a default case is present.
+  int c = 1;
+  switch (c) {
+  case 1:
+  case 2:
+  case 3:
+  default:
+break;
+  }
+
+  bool Flag = false;
+  switch (Flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: switch with only one case; use an if statement
+  case true:
+break;
+  }
+
+  switch (Flag) {
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: degenerated switch with default label only
+  default:
+break;
+  }
+
+  // This `switch` will create a frontend warning from '-Wswitch-bool' but is
+  // ok for this check.
+  switch (Flag) {
+  case true:
+break;
+  case false:
+break;
+  }
+}
+
+OS return_enumerator() {
+  return Linux;
+}
+
+// Enumpaths are already covered by a warning, this is just to ensure, that there is
+// no interference or fals