[-Wunreachable-code] Handle idiomatic do...while() with an uninteresting condition.

Sometimes do..while() is used to create a scope that can be left early.
In such cases, the unreachable 'while()' test is not usually interesting
unless it actually does something that is observable.

llvm-svn: 203036

1 files changed, 24 insertions, 2 deletions

diff --git a/clang/test/Sema/warn-unreachable.c b/clang/test/Sema/warn-unreachable.c
index 3c6d891613a..bf1e9137eb2 100644
--- a/clang/test/Sema/warn-unreachable.c
+++ b/clang/test/Sema/warn-unreachable.c
@@ -268,9 +268,31 @@ int test_MyEnum() {
     return 2; // no-warning
   if (ME_B)
     return 3;
-  // FIXME: we should only need one diagnostic here.
   if (!ME_B) // expected-warning {{will never be executed}}
-    return 4;// expected-warning {{will never be executed}}
+    return 4; // expected-warning {{will never be executed}}
   return 5;
 }
 
+// Test for idiomatic do..while.
+int test_do_while(int x) {
+  do {
+    if (x == calledFun())
+      break;
+    ++x;
+    break;
+  }
+  while (0); // no-warning
+  return x;
+}
+
+int test_do_while_nontrivial_cond(int x) {
+  do {
+    if (x == calledFun())
+      break;
+    ++x;
+    break;
+  }
+  while (calledFun()); // expected-warning {{will never be executed}}
+  return x;
+}
+