aaron.ballman created this revision.
aaron.ballman added reviewers: rsmith, dblaikie.
aaron.ballman added a subscriber: cfe-commits.
Herald added a subscriber: aemerson.
The va_start macro currently diagnoses passing a reference as the second
argument (the one representing the parameter before the ellipsis) because this
is undefined behavior in C++. This patch extends the checking to cover
additional cases of undefined behavior in both C and C++. The C11 Standard,
7.16.1.4p4 states, in part:
If the parameter parmN is declared with the register storage class, with a
function or array type, or with a type that is not compatible with the type
that results after application of the default argument promotions, the behavior
is undefined.
(This is picked up by reference in C++ under [support.runtime]p3.)
This patch adds a check for default argument promotions as well as parameters
declared with the register storage class. This helps cover some more of the
CERT secure coding rule EXP58-CPP. Pass an object of the correct type to
va_start
(https://www.securecoding.cert.org/confluence/display/cplusplus/EXP58-CPP.+Pass+an+object+of+the+correct+type+to+va_start).
http://reviews.llvm.org/D19244
Files:
include/clang/Basic/DiagnosticSemaKinds.td
lib/Sema/SemaChecking.cpp
test/Sema/varargs-x86-64.c
test/Sema/varargs.c
Index: test/Sema/varargs.c
===================================================================
--- test/Sema/varargs.c
+++ test/Sema/varargs.c
@@ -18,12 +18,11 @@
__builtin_va_start(ap, b);
}
-void f3(float a, ...)
-{
+void f3(float a, ...) { // expected-note 2{{parameter of type 'float' is declared here}}
__builtin_va_list ap;
- __builtin_va_start(ap, a);
- __builtin_va_start(ap, (a));
+ __builtin_va_start(ap, a); // expected-warning {{'va_start' has undefined behavior with types that undergo default argument promotion}}
+ __builtin_va_start(ap, (a)); // expected-warning {{'va_start' has undefined behavior with types that undergo default argument promotion}}
}
@@ -83,3 +82,21 @@
i = __builtin_va_start(ap, a); // expected-error {{assigning to 'int' from incompatible type 'void'}}
__builtin_va_end(ap);
}
+
+void f11(float f, ...) { // expected-note {{parameter of type 'float' is declared here}}
+ __builtin_va_list ap;
+ __builtin_va_start(ap, f); // expected-warning {{'va_start' has undefined behavior with types that undergo default argument promotion}}
+ __builtin_va_end(ap);
+}
+
+void f12(short s, ...) { // expected-note {{parameter of type 'short' is declared here}}
+ __builtin_va_list ap;
+ __builtin_va_start(ap, s); // expected-warning {{'va_start' has undefined behavior with types that undergo default argument promotion}}
+ __builtin_va_end(ap);
+}
+
+void f13(register int i, ...) { // expected-note {{parameter of type 'int' is declared here}}
+ __builtin_va_list ap;
+ __builtin_va_start(ap, i); // expected-warning {{'va_start' has undefined behavior with an object declared with the register storage class}}
+ __builtin_va_end(ap);
+}
Index: test/Sema/varargs-x86-64.c
===================================================================
--- test/Sema/varargs-x86-64.c
+++ test/Sema/varargs-x86-64.c
@@ -26,11 +26,11 @@
__builtin_ms_va_start(ap, b);
}
-void __attribute__((ms_abi)) g3(float a, ...) {
+void __attribute__((ms_abi)) g3(float a, ...) { // expected-note 2{{parameter of type 'float' is declared here}}
__builtin_ms_va_list ap;
- __builtin_ms_va_start(ap, a);
- __builtin_ms_va_start(ap, (a));
+ __builtin_ms_va_start(ap, a); // expected-warning {{'va_start' has undefined behavior with types that undergo default argument promotion}}
+ __builtin_ms_va_start(ap, (a)); // expected-warning {{'va_start' has undefined behavior with types that undergo default argument promotion}}
}
void __attribute__((ms_abi)) g5() {
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -2702,6 +2702,7 @@
// block.
QualType Type;
SourceLocation ParamLoc;
+ bool IsRegister = false;
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Arg)) {
if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(DR->getDecl())) {
@@ -2718,6 +2719,7 @@
Type = PV->getType();
ParamLoc = PV->getLocation();
+ IsRegister = PV->getStorageClass() == SC_Register;
}
}
@@ -2724,9 +2726,13 @@
if (!SecondArgIsLastNamedArgument)
Diag(TheCall->getArg(1)->getLocStart(),
diag::warn_second_arg_of_va_start_not_last_named_param);
- else if (Type->isReferenceType()) {
- Diag(Arg->getLocStart(),
- diag::warn_va_start_of_reference_type_is_undefined);
+ else if (IsRegister || Type->isReferenceType() ||
+ Type->isPromotableIntegerType() ||
+ Type->isSpecificBuiltinType(BuiltinType::Float)) {
+ unsigned Reason = 0;
+ if (Type->isReferenceType()) Reason = 1;
+ else if (IsRegister) Reason = 2;
+ Diag(Arg->getLocStart(), diag::warn_va_start_type_is_undefined) << Reason;
Diag(ParamLoc, diag::note_parameter_type) << Type;
}
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -7414,8 +7414,11 @@
def warn_second_arg_of_va_start_not_last_named_param : Warning<
"second argument to 'va_start' is not the last named parameter">,
InGroup<Varargs>;
-def warn_va_start_of_reference_type_is_undefined : Warning<
- "'va_start' has undefined behavior with reference types">, InGroup<Varargs>;
+def warn_va_start_type_is_undefined : Warning<
+ "'va_start' has undefined behavior with "
+ "%select{types that undergo default argument promotion|reference types|"
+ "an object declared with the register storage class}0">,
+ InGroup<Varargs>;
def err_first_argument_to_va_arg_not_of_type_va_list : Error<
"first argument to 'va_arg' is of type %0 and not 'va_list'">;
def err_second_parameter_to_va_arg_incomplete: Error<
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