[compiler-rt] [asan] Add test for deferencing zero-sized malloc/calloc (PR #155933)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Thurston Dang (thurstond)

<details>
<summary>Changes</summary>

ASan fails to catch this, because 0-byte allocations are converted into 1-byte allocations.

Bug originally reported by dvyukov

---
Full diff: https://github.com/llvm/llvm-project/pull/155933.diff


1 Files Affected:

- (added) compiler-rt/test/asan/TestCases/zero_alloc.cpp (+37) 


``````````diff
diff --git a/compiler-rt/test/asan/TestCases/zero_alloc.cpp b/compiler-rt/test/asan/TestCases/zero_alloc.cpp
new file mode 100644
index 0000000000000..3decd5acb7bae
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/zero_alloc.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_asan -Wno-alloc-size -fsanitize-recover=address %s -o %t && %env_asan_opts=halt_on_error=0 %run %t 2>&1 | FileCheck %s
+
+// XFAIL: *
+
+#include <malloc.h>
+#include <stdio.h>
+
+int main(int argc, char **argv) {
+  {
+     char* p1 = (char*)calloc(1, 0);
+     printf ("p1 is %p\n", p1);
+     printf ("Content of p1 is: %d\n", *p1);
+     // CHECK: ERROR: AddressSanitizer: heap-buffer-overflow
+     // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+     free(p1);
+  }
+
+  {
+     char* p2 = (char*)calloc(0, 1);
+     printf ("p2 is %p\n", p2);
+     printf ("Content of p2 is: %d\n", *p2);
+     // CHECK: ERROR: AddressSanitizer: heap-buffer-overflow
+     // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+     free(p2);
+  }
+
+  {
+     char* p3 = (char*)malloc(0);
+     printf ("p3 is %p\n", p3);
+     printf ("Content of p2 is: %d\n", *p3);
+     // CHECK: ERROR: AddressSanitizer: heap-buffer-overflow
+     // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+     free(p3);
+  }
+
+  return 0;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/155933