Teach -Wuninitialized to recognize __attribute__((analyzer_noreturn))

for halting the propagation of uninitialized value tracking along
a path.  Unlike __attribute__((noreturn)), this attribute (which
is used by clients of the static analyzer) can be used to annotate
functions that essentially never return, but in rare cares may be
allowed to return for (special) debugging purposes.  This attribute
has been shown in reducing false positives in the static analyzer
by pruning false postives, and is equally applicable here.

Handling this attribute in the CFG itself is another option, but
this is not something all clients (e.g., possibly -Wunreachable-code)
would want to see.

Addresses <rdar://problem/12281583>.

llvm-svn: 163681

1 files changed, 23 insertions, 0 deletions

diff --git a/clang/test/Sema/uninit-variables.c b/clang/test/Sema/uninit-variables.c
index 634ae0dc428..9e3dd9d2875 100644
--- a/clang/test/Sema/uninit-variables.c
+++ b/clang/test/Sema/uninit-variables.c
@@ -508,3 +508,26 @@ int self_init_in_cond(int *p) {
   int n = ((p && (0 || 1)) && (n = *p)) ? n : -1; // ok
   return n;
 }
+
+void test_analyzer_noreturn_aux() __attribute__((analyzer_noreturn));
+
+void test_analyzer_noreturn(int y) {
+  int x; // expected-note {{initialize the variable 'x' to silence this warning}}
+  if (y) {
+    test_analyzer_noreturn_aux();
+	++x; // no-warning
+  }
+  else {
+	++x; // expected-warning {{variable 'x' is uninitialized when used here}}
+  }
+}
+void test_analyzer_noreturn_2(int y) {
+  int x;
+  if (y) {
+    test_analyzer_noreturn_aux();
+  }
+  else {
+	x = 1;
+  }
+  ++x; // no-warning
+}