https://github.com/a-tarasyuk updated https://github.com/llvm/llvm-project/pull/135573
>From 93c8fc7faba6ab9537039b8745e62f5d79785cd0 Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Thu, 17 Apr 2025 23:58:35 +0300 Subject: [PATCH 1/6] [Clang] enhance loop analysis to handle variable changes inside lambdas --- clang/docs/ReleaseNotes.rst | 2 ++ clang/lib/Sema/SemaStmt.cpp | 19 ++++++++++-- clang/test/SemaCXX/warn-loop-analysis.cpp | 35 +++++++++++++++++++++++ 3 files changed, 54 insertions(+), 2 deletions(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index c75d83a6d1a7a..8a330c010a73d 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -385,6 +385,8 @@ Improvements to Clang's diagnostics Fixes #GH131127 +- The ``-Wloop-analysis`` warning now handles variable modifications inside lambda expressions (#GH132038). + Improvements to Clang's time-trace ---------------------------------- diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp index 39c2e157591df..2bb46dd94cca2 100644 --- a/clang/lib/Sema/SemaStmt.cpp +++ b/clang/lib/Sema/SemaStmt.cpp @@ -2002,9 +2002,24 @@ namespace { } void VisitDeclRefExpr(DeclRefExpr *E) { - if (VarDecl *VD = dyn_cast<VarDecl>(E->getDecl())) + if (VarDecl *VD = dyn_cast<VarDecl>(E->getDecl())) { if (Decls.count(VD)) FoundDecl = true; + } else if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getDecl()); + MD && isLambdaCallOperator(MD)) { + for (const auto &Capture : MD->getParent()->captures()) { + if (!Capture.capturesVariable()) + continue; + + LambdaCaptureKind CK = Capture.getCaptureKind(); + if (CK != LCK_ByRef) + continue; + + VarDecl *VD = dyn_cast<VarDecl>(Capture.getCapturedVar()); + if (VD && Decls.count(VD)) + FoundDecl = true; + } + } } void VisitPseudoObjectExpr(PseudoObjectExpr *POE) { @@ -2021,7 +2036,7 @@ namespace { bool FoundDeclInUse() { return FoundDecl; } - }; // end class DeclMatcher + }; // end class DeclMatcher void CheckForLoopConditionalStatement(Sema &S, Expr *Second, Expr *Third, Stmt *Body) { diff --git a/clang/test/SemaCXX/warn-loop-analysis.cpp b/clang/test/SemaCXX/warn-loop-analysis.cpp index 324dd386292ac..ec2894a46ee77 100644 --- a/clang/test/SemaCXX/warn-loop-analysis.cpp +++ b/clang/test/SemaCXX/warn-loop-analysis.cpp @@ -299,3 +299,38 @@ void test10() { for (auto[i, j, k] = arr; i < a; ++i) { } for (auto[i, j, k] = arr; i < a; ++arr[0]) { } }; + +namespace GH132038 { +extern void foo(int); +void test1() { + int a = 0; + auto incr_a = [&a]() { ++a; }; + + for (int b = 10; a <= b; incr_a()) + foo(a); + + for (int b = 10; a <= b;) + incr_a(); + + for (int b = 10; a <= b; [&a]() { ++a; }()) { } + for (int b = 10; a <= b; [&a]() { }()) { } +} + +void test2() { + int a = 0; + auto incr_a = [a]() { }; + auto incr_b = [](int b) { }; + + for (int b = 10; a <= b; incr_a()) // expected-warning {{variables 'a' and 'b' used in loop condition not modified in loop body}} + foo(a); + + for (int b = 10; a <= b;) // expected-warning {{variables 'a' and 'b' used in loop condition not modified in loop body}} + incr_a(); + + for (int b = 10; a <= b; incr_b(b)) // expected-warning {{variables 'a' and 'b' used in loop condition not modified in loop body}} + foo(a); + + for (int b = 10; a <= b;) // expected-warning {{variables 'a' and 'b' used in loop condition not modified in loop body}} + incr_b(b); +} +} >From 00053790db55d3f26836e958f8624c0f4bf4fbb8 Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Fri, 18 Apr 2025 18:28:16 +0300 Subject: [PATCH 2/6] add FIXME test case --- clang/test/SemaCXX/warn-loop-analysis.cpp | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/clang/test/SemaCXX/warn-loop-analysis.cpp b/clang/test/SemaCXX/warn-loop-analysis.cpp index ec2894a46ee77..7773bef0cd238 100644 --- a/clang/test/SemaCXX/warn-loop-analysis.cpp +++ b/clang/test/SemaCXX/warn-loop-analysis.cpp @@ -318,8 +318,11 @@ void test1() { void test2() { int a = 0; + int *c = &a; + auto incr_a = [a]() { }; auto incr_b = [](int b) { }; + auto incr_c = [c]() { ++*c; }; for (int b = 10; a <= b; incr_a()) // expected-warning {{variables 'a' and 'b' used in loop condition not modified in loop body}} foo(a); @@ -332,5 +335,9 @@ void test2() { for (int b = 10; a <= b;) // expected-warning {{variables 'a' and 'b' used in loop condition not modified in loop body}} incr_b(b); + + // FIXME: handle modification of loop control variable inside lambda body + for (a = 10; a <= 20; incr_c()) // expected-warning {{variable 'a' used in loop condition not modified in loop body}} + foo(a); } } >From 5f3e4609d28a65e326eaa0a0b6c7ad13f886b92f Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Wed, 7 Jan 2026 15:29:49 +0200 Subject: [PATCH 3/6] add FIXME for lambda edge case --- clang/lib/Sema/SemaStmt.cpp | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp index ffb527bfbfa6d..1e8ea1ebc513d 100644 --- a/clang/lib/Sema/SemaStmt.cpp +++ b/clang/lib/Sema/SemaStmt.cpp @@ -2001,6 +2001,15 @@ namespace { FoundDecl = true; } else if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getDecl()); MD && isLambdaCallOperator(MD)) { + // FIXME: This has limitations handling updates to the loop control + // variable that occur indirectly inside a lambda called from the loop + // body. For example: + // + // int a = 0; + // int *c = &a; + // auto incr_c = [c]() { ++*c; }; + // for (a = 10; a <= 20; incr_c()) + // foo(a); for (const auto &Capture : MD->getParent()->captures()) { if (!Capture.capturesVariable()) continue; >From 8378dd070e95ee20b95edce55fa1db5d68989fc8 Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Wed, 7 Jan 2026 15:30:27 +0200 Subject: [PATCH 4/6] clarify -Wloop-analysis ReleaseNotes --- clang/docs/ReleaseNotes.rst | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index da45f9aaf6b28..a16f279fe2f2b 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -498,7 +498,8 @@ Improvements to Clang's diagnostics - Clang now generates a fix-it for C++20 designated initializers when the initializers do not match the declaration order in the structure. -- The ``-Wloop-analysis`` warning now handles variable modifications inside lambda expressions (#GH132038). +- The ``-Wloop-analysis`` warning has been extended to catch more cases of + variable modification inside lambda expressions (#GH132038). Improvements to Clang's time-trace ---------------------------------- >From 1fdab0eae4864a8fe85cf3c11cbfaba3cbe2f6a0 Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Wed, 7 Jan 2026 15:31:39 +0200 Subject: [PATCH 5/6] cleanup --- clang/lib/Sema/SemaStmt.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp index 1e8ea1ebc513d..1c0f5f2783541 100644 --- a/clang/lib/Sema/SemaStmt.cpp +++ b/clang/lib/Sema/SemaStmt.cpp @@ -2039,7 +2039,7 @@ namespace { bool FoundDeclInUse() { return FoundDecl; } - }; // end class DeclMatcher + }; // end class DeclMatcher void CheckForLoopConditionalStatement(Sema &S, Expr *Second, Expr *Third, Stmt *Body) { >From c8207173433706cab119a7889c3ac399cb8b0172 Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Fri, 13 Feb 2026 16:03:46 +0200 Subject: [PATCH 6/6] prefer const auto for for dyn_cast results --- clang/lib/Sema/SemaStmt.cpp | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp index 1c0f5f2783541..106ca21e712f9 100644 --- a/clang/lib/Sema/SemaStmt.cpp +++ b/clang/lib/Sema/SemaStmt.cpp @@ -1996,10 +1996,10 @@ namespace { } void VisitDeclRefExpr(DeclRefExpr *E) { - if (VarDecl *VD = dyn_cast<VarDecl>(E->getDecl())) { + if (const auto *VD = dyn_cast<VarDecl>(E->getDecl())) { if (Decls.count(VD)) FoundDecl = true; - } else if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getDecl()); + } else if (const auto *MD = dyn_cast<CXXMethodDecl>(E->getDecl()); MD && isLambdaCallOperator(MD)) { // FIXME: This has limitations handling updates to the loop control // variable that occur indirectly inside a lambda called from the loop @@ -2018,7 +2018,7 @@ namespace { if (CK != LCK_ByRef) continue; - VarDecl *VD = dyn_cast<VarDecl>(Capture.getCapturedVar()); + const auto *VD = dyn_cast<VarDecl>(Capture.getCapturedVar()); if (VD && Decls.count(VD)) FoundDecl = true; } _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
