[ASan] Allow new/delete replacement by making interceptors weak

[hctim]

Summary

ASan declares these functions as strongly-defined, which results in
'duplicate symbol' errors when trying to replace them in user code when
linking the runtimes statically.

[eugenis]

Add it to CXX_OPERATOR_ATTRIBUTE, on non-mac non-windows?

[hctim]

In D100220#2680431, @eugenis wrote:

Add it to CXX_OPERATOR_ATTRIBUTE, on non-mac non-windows?

Done.

[hctim]

wrong diffbase messed up phabricator rendering

[eugenis]

LGTM

[morehouse]

compiler-rt/test/asan/TestCases/replaceable_new_delete.cpp

1

This test is failing on Windows: https://lab.llvm.org/buildbot/#/builders/127/builds/9062

[hctim]

compiler-rt/test/asan/TestCases/replaceable_new_delete.cpp

1

Thanks, submitted 15689f3af018c420403bb0fd0df0aa5f79796b94 to disable this test on windows. I think the issue can be permanently solved using some of the SANITIZER_INTERFACE_WEAK_DEF(ReturnType, Name, ...) macros in compiler-rt, but I don't have a Windows machine to test on.

The test disablement on Windows is fine, it just means that Windows isn't getting the new replaceable behaviour.

compiler-rt/lib/asan/asan_new_delete.cpp

 COMMENT_EXPORT("??2@YAPAXIABUnothrow_t@std@@@Z")  // operator new nothrow
 COMMENT_EXPORT("??3@YAXPAX@Z")                    // operator delete
 COMMENT_EXPORT("??3@YAXPAXI@Z")                   // sized operator delete
 COMMENT_EXPORT("??_U@YAPAXI@Z")                   // operator new[]
 COMMENT_EXPORT("??_V@YAXPAX@Z")                   // operator delete[]
 #endif
 #undef COMMENT_EXPORT
 #else
-#define CXX_OPERATOR_ATTRIBUTE INTERCEPTOR_ATTRIBUTE
+#define CXX_OPERATOR_ATTRIBUTE INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 #endif
 
 using namespace __asan;
 
 // FreeBSD prior v9.2 have wrong definition of 'size_t'.
 // http://svnweb.freebsd.org/base?view=revision&revision=232261
 #if SANITIZER_FREEBSD && SANITIZER_WORDSIZE == 32
 #include <sys/param.h>

compiler-rt/test/asan/TestCases/replaceable_new_delete.cpp

+// Ensure that operator new/delete are still replaceable.
+
+// RUN: %clangxx %s -o %t -fsanitize=address -shared-libsan && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx %s -o %t -fsanitize=address -static-libsan && not %run %t 2>&1 | FileCheck %s
+
+#include <cstdio>
+#include <cstdlib>
+#include <new>
+
+void *operator new[](size_t size) {
+  fprintf(stderr, "replaced new\n");
+  return malloc(size);
+}
+
+void operator delete[](void *ptr) noexcept {
+  fprintf(stderr, "replaced delete\n");
+  return free(ptr);
+}
+
+int main(int argc, char **argv) {
+  // CHECK: replaced new
+  char *x = new char[5];
+  // CHECK: replaced delete
+  delete[] x;
+  // CHECK: ERROR: AddressSanitizer
+  *x = 13;
+  return 0;
+}