[OpenMP] diagnose assign to firstprivate const, patch by Joel E. Denny

Summary:
[OpenMP] diagnose assign to firstprivate const

Clang does not diagnose assignments to const variables declared
firstprivate.  Furthermore, codegen is broken such that, at run time,
such assignments simply have no effect.  For example, the following
prints 0 not 1:

int main() {
  const int i = 0;
  #pragma omp parallel firstprivate(i)
  { i=1; printf("%d\n", i); }
  return 0;
}

This commit makes these assignments a compile error, which is
consistent with other OpenMP compilers I've tried (pgcc 17.4-0, gcc
6.3.0).

Reviewers: ABataev

Reviewed By: ABataev

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D39859

llvm-svn: 317891

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index d5a7bc3..f895e0f 100644 (file)
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -14352,8 +14352,13 @@ static bool captureInCapturedRegion(CapturedRegionScopeInfo *RSI,
   bool ByRef = true;
   // Using an LValue reference type is consistent with Lambdas (see below).
   if (S.getLangOpts().OpenMP && RSI->CapRegionKind == CR_OpenMP) {
-    if (S.IsOpenMPCapturedDecl(Var))
+    if (S.IsOpenMPCapturedDecl(Var)) {
+      bool HasConst = DeclRefType.isConstQualified();
       DeclRefType = DeclRefType.getUnqualifiedType();
+      // Don't lose diagnostics about assignments to const.
+      if (HasConst)
+        DeclRefType.addConst();
+    }
     ByRef = S.IsOpenMPCapturedByRef(Var, RSI->OpenMPLevel);
   }
 

diff --git a/clang/test/OpenMP/parallel_firstprivate_messages.cpp b/clang/test/OpenMP/parallel_firstprivate_messages.cpp
index fc0eb4c..b2cb4ff 100644 (file)
--- a/clang/test/OpenMP/parallel_firstprivate_messages.cpp
+++ b/clang/test/OpenMP/parallel_firstprivate_messages.cpp
@@ -56,7 +56,7 @@ using A::x;
 }
 
 int main(int argc, char **argv) {
-  const int d = 5;
+  const int d = 5; // expected-note {{variable 'd' declared const here}}
   const int da[5] = { 0 };
   S4 e(4);
   S5 g(5);
@@ -72,6 +72,8 @@ int main(int argc, char **argv) {
   #pragma omp parallel firstprivate (argc)
   #pragma omp parallel firstprivate (S1) // expected-error {{'S1' does not refer to a value}}
   #pragma omp parallel firstprivate (a, b, c, d, f) // expected-error {{firstprivate variable with incomplete type 'S1'}}
+  #pragma omp parallel firstprivate (d)
+    d = 5; // expected-error {{cannot assign to variable 'd' with const-qualified type}}
   #pragma omp parallel firstprivate (argv[1]) // expected-error {{expected variable name}}
   #pragma omp parallel firstprivate(ba)
   #pragma omp parallel firstprivate(ca)