[OPENMP]Initial fix PR42392: Improve -Wuninitialized warnings for OpenMP programs.

Summary:
Some OpenMP clauses rely on the values of the variables. If the variable
is not initialized and used in OpenMP clauses that depend on the
variables values, it should be reported that the uninitialized variable
is used in the OpenMP clause expression.
This patch adds initial processing for uninitialized variables in OpenMP
constructs. Currently, it checks for use of the uninitialized variables
in the structured blocks.

Reviewers: NoQ, Szelethus, dcoughlin, xazax.hun, a.sidorin, george.karpenkov, szepet

Subscribers: rnkovacs, guansong, jfb, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64356

llvm-svn: 365786

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/test/OpenMP/for_misc_messages.c b/clang/test/OpenMP/for_misc_messages.c
index e36a1c6db01..324c70bee31 100644
--- a/clang/test/OpenMP/for_misc_messages.c
+++ b/clang/test/OpenMP/for_misc_messages.c
@@ -2,6 +2,13 @@
 
 // RUN: %clang_cc1 -fsyntax-only -fopenmp-simd -triple x86_64-unknown-unknown -verify %s -Wuninitialized
 
+void xxx(int argc) {
+  int x; // expected-note {{initialize the variable 'x' to silence this warning}}
+#pragma omp for
+  for (int i = 0; i < 10; ++i)
+    argc = x; // expected-warning {{variable 'x' is uninitialized when used here}}
+}
+
 // expected-error@+1 {{unexpected OpenMP directive '#pragma omp for'}}
 #pragma omp for