r317891 - [OpenMP] diagnose assign to firstprivate const, patch by Joel E. Denny

[Alexey Bataev via cfe-commits]

Author: abataev
Date: Fri Nov 10 07:39:50 2017
New Revision: 317891

URL: http://llvm.org/viewvc/llvm-project?rev=317891&view=rev
Log:
[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

Modified:
    cfe/trunk/lib/Sema/SemaExpr.cpp
    cfe/trunk/test/OpenMP/parallel_firstprivate_messages.cpp

Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=317891&r1=317890&r2=317891&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Fri Nov 10 07:39:50 2017
@@ -14352,8 +14352,13 @@ static bool captureInCapturedRegion(Capt
   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);
   }
 

Modified: cfe/trunk/test/OpenMP/parallel_firstprivate_messages.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/OpenMP/parallel_firstprivate_messages.cpp?rev=317891&r1=317890&r2=317891&view=diff
==============================================================================
--- cfe/trunk/test/OpenMP/parallel_firstprivate_messages.cpp (original)
+++ cfe/trunk/test/OpenMP/parallel_firstprivate_messages.cpp Fri Nov 10 07:39:50 2017
@@ -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)