cstddef is needed for size_t definition.
(Multiple headers can provide size_t but none of them exists.)
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D96213
If we define memcmp in an archive, bcmp should be defined as well (many libc
define bcmp/memcmp in one object file). Otherwise if the application calls bcmp
or strcmp which gets optimized to bcmp (SimplifyLibCalls), the undefined
reference may pull in an optimized bcmp/strcmp implementation (libc replacement)
later on the linker command line. If both libFuzzer's memcmp and the optimized
memcmp are strong => there will be a multiple definition error.
Summary: libFuzzer intercepts certain library functions such as memcmp/strcmp by defining weak hooks. Weak hooks, however, are called only when other runtimes such as ASan is linked. This patch defines libFuzzer's own interceptors, which is linked into the libFuzzer executable when other runtimes are not linked, i.e., when -fsanitize=fuzzer is given, but not others.
The patch once landed but was reverted in 8ef9e2bf35 due to an assertion failure caused by calling an intercepted function, strncmp, while initializing the interceptors in fuzzerInit(). This issue is now fixed by calling libFuzzer's own implementation of library functions (i.e., internal_*) when the fuzzer has not been initialized yet, instead of recursively calling fuzzerInit() again.
Reviewers: kcc, morehouse, hctim
Subscribers: #sanitizers, krytarowski, mgorny, cfe-commits
Tags: #clang, #sanitizers
Differential Revision: https://reviews.llvm.org/D83494
This causes binaries linked with this runtime to crash on startup if
dlsym uses any of the intercepted functions. (For example, that happens
when using tcmalloc as the allocator: dlsym attempts to allocate memory
with malloc, and tcmalloc uses strncmp within its implementation.)
Also revert dependent commit "[libFuzzer] Disable implicit builtin knowledge about memcmp-like functions when -fsanitize=fuzzer-no-link is given."
This reverts commit f78d9fceea and 12d1124c49.
Summary: libFuzzer intercepts certain library functions such as memcmp/strcmp by defining weak hooks. Weak hooks, however, are called only when other runtimes such as ASan is linked. This patch defines libFuzzer's own interceptors, which is linked into the libFuzzer executable when other runtimes are not linked, i.e., when -fsanitize=fuzzer is given, but not others.
Reviewers: kcc, morehouse, hctim
Reviewed By: morehouse, hctim
Subscribers: krytarowski, mgorny, cfe-commits, #sanitizers
Tags: #clang, #sanitizers
Differential Revision: https://reviews.llvm.org/D83494
Khem Raj