add explicit test for stack smashing

Author: nickdesaulniers

libc/test/src/compiler/CMakeLists.txt

@@ -8,4 +8,7 @@ add_libc_unittest(
     stack_chk_guard_test.cpp
   DEPENDS
     libc.src.compiler.__stack_chk_fail
+    libc.src.string.memset
+  COMPILE_OPTIONS
+    -fstack-protector-all
   )

libc/test/src/compiler/stack_chk_guard_test.cpp

@@ -9,8 +9,16 @@
 #include "llvm-libc-macros/signal-macros.h"
 #include "src/compiler/__stack_chk_fail.h"
 #include "test/UnitTest/Test.h"
+#include "src/string/memset.h"
 
 TEST(LlvmLibcStackChkFail, Death) {
   EXPECT_DEATH([] { LIBC_NAMESPACE::__stack_chk_fail(); },
                WITH_SIGNAL(SIGABRT));
 }
+
+TEST(LlvmLibcStackChkFail, Smash) {
+  EXPECT_DEATH([] {
+    int arr [20];
+    LIBC_NAMESPACE::memset(arr, 0xAA, 9001);
+  }, WITH_SIGNAL(SIGABRT));
+}