[analyzer] Buffers passed to CGBitmapContextCreate can escape.

Specifically, although the bitmap context does not take ownership of the
buffer (unlike CGBitmapContextCreateWithData), the data buffer can be extracted
out of the created CGContextRef. Thus the buffer is not leaked even if its
original pointer goes out of scope, as long as
- the context escapes, or
- it is retrieved via CGBitmapContextGetData and freed.

Actually implementing that logic is beyond the current scope of MallocChecker,
so for now CGBitmapContextCreate goes on our system function exception list.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158579 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/test/Analysis/malloc.c b/test/Analysis/malloc.c
index 7c2196ac9e..c532d6813f 100644
--- a/test/Analysis/malloc.c
+++ b/test/Analysis/malloc.c
@@ -955,3 +955,22 @@ void test_double_assign_ints_positive()
   (void*)(long)(unsigned long)ptr; // expected-warning {{unused}} expected-warning {{leak}}
 }
 
+
+void testCGContextNoLeak()
+{
+  void *ptr = malloc(16);
+  CGContextRef context = CGBitmapContextCreate(ptr);
+
+  // Because you can get the data back out like this, even much later,
+  // CGBitmapContextCreate is one of our "stop-tracking" exceptions.
+  free(CGBitmapContextGetData(context));
+}
+
+void testCGContextLeak()
+{
+  void *ptr = malloc(16);
+  CGContextRef context = CGBitmapContextCreate(ptr);
+  // However, this time we're just leaking the data, because the context
+  // object doesn't escape and it hasn't been freed in this function.
+}
+