[PATCH] D83494: [libFuzzer] Link libFuzzer's own interceptors when other compiler runtimes are not linked.

[Matt Morehouse via Phabricator via cfe-commits]

morehouse added a comment.

In D83494#2150946 <https://reviews.llvm.org/D83494#2150946>, @dokyungs wrote:

> I was misled; the error is actually ambiguating new "declarations", not definitions. The exact error message goes like:
>
>   error: ambiguating new declaration of ‘char* strcasestr(const char*, const char*)’
>     104 | ATTRIBUTE_INTERFACE char *strcasestr(const char *s1, const char *s2) {
>         |                           ^~~~~~~~~~
>   In file included from include/c++/v1/string.h:60,
>                    from include/c++/v1/cstring:60,
>                    from include/c++/v1/algorithm:641,
>                    from include/c++/v1/__string:57,
>                    from include/c++/v1/string_view:175,
>                    from include/c++/v1/string:506,
>                    from FuzzerInterceptors.cpp:14:
>   /usr/include/string.h:356:26: note: old declaration ‘const char* strcasestr(const char*, const char*)’
>     356 | extern "C++" const char *strcasestr (const char *__haystack,
>         |                          ^~~~~~~~~~
>
>
> C++'s declarations of strstr/strcasestr each have two different versions (const v. non const), and neither of them matches C's strstr/strcasestr declarations. So I could either (i) make libFuzzer's declarations of strstr/strcasestr match one of C++ versions (for this reason there was "extern C++ ..."), or (ii) make them match C declarations of strstr/strcasestr and remove C++ declarations by not including string.h. I realized that (ii) is a simpler solution, so I changed the code that way.


Got it.  We only need to intercept the libc version of `strstr`.  We don't care about libc++ since that one just forwards to libc.  So I think this is the right approach.



================
Comment at: compiler-rt/lib/fuzzer/FuzzerDefs.h:23
 
-
-// Platform detection.
-#ifdef __linux__
-#define LIBFUZZER_APPLE 0
-#define LIBFUZZER_FUCHSIA 0
-#define LIBFUZZER_LINUX 1
-#define LIBFUZZER_NETBSD 0
-#define LIBFUZZER_FREEBSD 0
-#define LIBFUZZER_OPENBSD 0
-#define LIBFUZZER_WINDOWS 0
-#define LIBFUZZER_EMSCRIPTEN 0
-#elif __APPLE__
-#define LIBFUZZER_APPLE 1
-#define LIBFUZZER_FUCHSIA 0
-#define LIBFUZZER_LINUX 0
-#define LIBFUZZER_NETBSD 0
-#define LIBFUZZER_FREEBSD 0
-#define LIBFUZZER_OPENBSD 0
-#define LIBFUZZER_WINDOWS 0
-#define LIBFUZZER_EMSCRIPTEN 0
-#elif __NetBSD__
-#define LIBFUZZER_APPLE 0
-#define LIBFUZZER_FUCHSIA 0
-#define LIBFUZZER_LINUX 0
-#define LIBFUZZER_NETBSD 1
-#define LIBFUZZER_FREEBSD 0
-#define LIBFUZZER_OPENBSD 0
-#define LIBFUZZER_WINDOWS 0
-#define LIBFUZZER_EMSCRIPTEN 0
-#elif __FreeBSD__
-#define LIBFUZZER_APPLE 0
-#define LIBFUZZER_FUCHSIA 0
-#define LIBFUZZER_LINUX 0
-#define LIBFUZZER_NETBSD 0
-#define LIBFUZZER_FREEBSD 1
-#define LIBFUZZER_OPENBSD 0
-#define LIBFUZZER_WINDOWS 0
-#define LIBFUZZER_EMSCRIPTEN 0
-#elif __OpenBSD__
-#define LIBFUZZER_APPLE 0
-#define LIBFUZZER_FUCHSIA 0
-#define LIBFUZZER_LINUX 0
-#define LIBFUZZER_NETBSD 0
-#define LIBFUZZER_FREEBSD 0
-#define LIBFUZZER_OPENBSD 1
-#define LIBFUZZER_WINDOWS 0
-#define LIBFUZZER_EMSCRIPTEN 0
-#elif _WIN32
-#define LIBFUZZER_APPLE 0
-#define LIBFUZZER_FUCHSIA 0
-#define LIBFUZZER_LINUX 0
-#define LIBFUZZER_NETBSD 0
-#define LIBFUZZER_FREEBSD 0
-#define LIBFUZZER_OPENBSD 0
-#define LIBFUZZER_WINDOWS 1
-#define LIBFUZZER_EMSCRIPTEN 0
-#elif __Fuchsia__
-#define LIBFUZZER_APPLE 0
-#define LIBFUZZER_FUCHSIA 1
-#define LIBFUZZER_LINUX 0
-#define LIBFUZZER_NETBSD 0
-#define LIBFUZZER_FREEBSD 0
-#define LIBFUZZER_OPENBSD 0
-#define LIBFUZZER_WINDOWS 0
-#define LIBFUZZER_EMSCRIPTEN 0
-#elif __EMSCRIPTEN__
-#define LIBFUZZER_APPLE 0
-#define LIBFUZZER_FUCHSIA 0
-#define LIBFUZZER_LINUX 0
-#define LIBFUZZER_NETBSD 0
-#define LIBFUZZER_FREEBSD 0
-#define LIBFUZZER_OPENBSD 0
-#define LIBFUZZER_WINDOWS 0
-#define LIBFUZZER_EMSCRIPTEN 1
-#else
-#error "Support for your platform has not been implemented"
-#endif
-
-#if defined(_MSC_VER) && !defined(__clang__)
-// MSVC compiler is being used.
-#define LIBFUZZER_MSVC 1
-#else
-#define LIBFUZZER_MSVC 0
-#endif
-
-#ifndef __has_attribute
-#  define __has_attribute(x) 0
-#endif
-
-#define LIBFUZZER_POSIX                                                        \
-  (LIBFUZZER_APPLE || LIBFUZZER_LINUX || LIBFUZZER_NETBSD ||                   \
-   LIBFUZZER_FREEBSD || LIBFUZZER_OPENBSD || LIBFUZZER_EMSCRIPTEN)
-
-#ifdef __x86_64
-#  if __has_attribute(target)
-#    define ATTRIBUTE_TARGET_POPCNT __attribute__((target("popcnt")))
-#  else
-#    define ATTRIBUTE_TARGET_POPCNT
-#  endif
-#else
-#  define ATTRIBUTE_TARGET_POPCNT
-#endif
-
-
-#ifdef __clang__  // avoid gcc warning.
-#  if __has_attribute(no_sanitize)
-#    define ATTRIBUTE_NO_SANITIZE_MEMORY __attribute__((no_sanitize("memory")))
-#  else
-#    define ATTRIBUTE_NO_SANITIZE_MEMORY
-#  endif
-#  define ALWAYS_INLINE __attribute__((always_inline))
-#else
-#  define ATTRIBUTE_NO_SANITIZE_MEMORY
-#  define ALWAYS_INLINE
-#endif // __clang__
-
-#if LIBFUZZER_WINDOWS
-#define ATTRIBUTE_NO_SANITIZE_ADDRESS
-#else
-#define ATTRIBUTE_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address))
-#endif
-
-#if LIBFUZZER_WINDOWS
-#define ATTRIBUTE_ALIGNED(X) __declspec(align(X))
-#define ATTRIBUTE_INTERFACE __declspec(dllexport)
-// This is used for __sancov_lowest_stack which is needed for
-// -fsanitize-coverage=stack-depth. That feature is not yet available on
-// Windows, so make the symbol static to avoid linking errors.
-#define ATTRIBUTES_INTERFACE_TLS_INITIAL_EXEC static
-#define ATTRIBUTE_NOINLINE __declspec(noinline)
-#else
-#define ATTRIBUTE_ALIGNED(X) __attribute__((aligned(X)))
-#define ATTRIBUTE_INTERFACE __attribute__((visibility("default")))
-#define ATTRIBUTES_INTERFACE_TLS_INITIAL_EXEC \
-  ATTRIBUTE_INTERFACE __attribute__((tls_model("initial-exec"))) thread_local
-
-#define ATTRIBUTE_NOINLINE __attribute__((noinline))
-#endif
-
-#if defined(__has_feature)
-#  if __has_feature(address_sanitizer)
-#    define ATTRIBUTE_NO_SANITIZE_ALL ATTRIBUTE_NO_SANITIZE_ADDRESS
-#  elif __has_feature(memory_sanitizer)
-#    define ATTRIBUTE_NO_SANITIZE_ALL ATTRIBUTE_NO_SANITIZE_MEMORY
-#  else
-#    define ATTRIBUTE_NO_SANITIZE_ALL
-#  endif
-#else
-#  define ATTRIBUTE_NO_SANITIZE_ALL
-#endif
+#include "FuzzerPlatform.h"
 
----------------
Nit: we should really not include this here.  Instead, we should include it directly in any libFuzzer file that needs the platform macros.

Of course, that will add some noise to this patch.  Could you splice this change into a separate patch that we can submit first?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83494/new/

https://reviews.llvm.org/D83494