C89 had a questionable feature where the compiler would implicitly
declare a function that the user called but was never previously
declared. The resulting function would be globally declared as
extern int func(); -- a function without a prototype which accepts zero
or more arguments.
C99 removed support for this questionable feature due to severe
security concerns. However, there was no deprecation period; C89 had
the feature, C99 didn't. So Clang (and GCC) both supported the
functionality as an extension in C99 and later modes.
C2x no longer supports that function signature as it now requires all
functions to have a prototype, and given the known security issues with
the feature, continuing to support it as an extension is not tenable.
This patch changes the diagnostic behavior for the
-Wimplicit-function-declaration warning group depending on the language
mode in effect. We continue to warn by default in C89 mode (due to the
feature being dangerous to use). However, because this feature will not
be supported in C2x mode, we've diagnosed it as being invalid for so
long, the security concerns with the feature, and the trivial
workaround for users (declare the function), we now default the
extension warning to an error in C99-C17 mode. This still gives users
an easy workaround if they are extensively using the extension in those
modes (they can disable the warning or use -Wno-error to downgrade the
error), but the new diagnostic makes it more clear that this feature is
not supported and should be avoided. In C2x mode, we no longer allow an
implicit function to be defined and treat the situation the same as any
other lookup failure.
Differential Revision: https://reviews.llvm.org/D122983
Like D118875, but for ubsan, asan, etc.
With this, I can successfully run:
bin/clang++ -target x86_64-apple-ios14.0-macabi foo.cc \
-isysroot $(xcrun -show-sdk-path) -fsanitize=undefined
with a locally built libclang_rt.ubsan_osx_dynamic.dylib.
Differential Revision: https://reviews.llvm.org/D124059
Makes
bin/llvm-lit \
projects/compiler-rt/test/profile/Profile-arm64/instrprof-darwin-dead-strip.c
pass on my machine.
Without this change, ld64 complains that the bitcode was generated by LLVM 15
while the reader is 13.1 -- the version of Xcode on my machine. Looks like the
DYLD_LIBRARY_PATH technique isn't working.
-lto_library was added back in ld64-136, which was in Xcode 4.6, which was
released over 10 years ago. So relying on it should be safe by now.
Differential Revision: https://reviews.llvm.org/D124018
1. Add correct pc, sp and bp for FreeBSD.
2. Since there's no personality.h header on FreeBSD, move SANITIZER_PPC64V2
case below FREEBSD case.
3. __ppc_get_timebase_freq() is glibc-specific. Add a shim for FreeBSD that
does the same.
Looks like when the VE support was added it was added a few lines below where it should have been.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D123439
Current check assumes iOS as the only Apple devices running arm64.
```#if SANITIZER_MAC && !(defined(__arm64__) && SANITIZER_IOS)```
Stops Apple Silicon from being flagged as requiring unique RTTI.
This introduced unexpected behavior within the sanitizer.
rdar://91446703
Differential Revision: https://reviews.llvm.org/D123736
Usually when we generated stacktraces the process is in error state, so
running hooks may crash the process and prevent meaningfull error report.
Symbolizer, unwinder and pthread are potential source of mallocs.
https://b.corp.google.com/issues/228110771
Reviewed By: kda
Differential Revision: https://reviews.llvm.org/D123566
This piece of code tries to implement the semantics "cross compile?" to
determine CFLAGS used for test binary compilation.
```
if(ANDROID OR ${arch} MATCHES "arm|aarch64|riscv32|riscv64")
```
Since Apple Silicon, macOS runs on arm64e, so we take the wrong branch
when compiling and running tests locally "on the host" on an AS machine.
Furthermore, for Apple code, we use the separate
`get_test_cflags_for_apple_platform` function to determine these test
compiliation flags and `get_test_cc_for_arch` is only ever used in the
"compile & run on host" case, so we can short-curcuit the "cross
compile?" check here.
rdar://91446703
Differential Revision: https://reviews.llvm.org/D123633
Usually when we generated stacktraces the process is in error state, so
running hooks may crash the process and prevent meaningfull error report.
Symbolizer, unwinder and pthread are potential source of mallocs.
https://b.corp.google.com/issues/228110771
Reviewed By: kda
Differential Revision: https://reviews.llvm.org/D123566
ld64 implicitly ad-hoc code-signs as of Xcode 12, and `strip` and friends know
how keep this special ad-hoc signature valid.
So this should have no effective behavior change, except that you can now strip
libclang_rt.asan_osx_dynamic.dylib and it'll still have a valid ad-hoc
signature, instead of strip printing "warning: changes being made to the file
will invalidate the code signature in:" and making the ad-hoc code signature
invalid.
Differential Revision: https://reviews.llvm.org/D123475
This reverts commit 63f2d1f4d4.
I don't quite understand why, but this causes a linker error for
me and a number of buildbots:
/home/npopov/repos/llvm-project/compiler-rt/lib/ubsan/../sanitizer_common/sanitizer_stacktrace.h:130: error: undefined reference to '__sanitizer::BufferedStackTrace::UnwindImpl(unsigned long, unsigned long, void*, bool, unsigned int)'
ubsan_GetStackTrace (from 52b751088b) called by
~ScopeReport leaves top/bottom zeroes in the
`!WillUseFastUnwind(request_fast_unwind)` code path.
When BufferedStackTrace::Unwind falls back to UnwindFast,
`if (stack_top < 4096) return;` will return early, leaving just one frame in the stack trace.
Fix this by always initializing top/bottom like 261d6e05d5.
Reviewed By: eugenis, yln
Differential Revision: https://reviews.llvm.org/D123562
Tested on an example callstack with misplaced binaries from Android.
Tested Regex against callstack without Build ID to confirm it still works.
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D123437
This keeps the test behavior unchanged when CLANG_DEFAULT_PIE_ON_LINUX switches
to ON by default.
Note: current clang --target=mips64el-linux-gnu -fpie -pie -fuse-ld=lld
does not link with C++ exceptions, using -pie would lead to
```
ld.lld: error: cannot preempt symbol: DW.ref.__gxx_personality_v0
...
ld.lld: error: relocation R_MIPS_64 cannot be used against local symbol; recompile with -fPIC
...
```
when linking `ScudoUnitTests`: https://lab.llvm.org/buildbot/#/builders/169/builds/7311/steps/18/logs/stdio
According to the RFC [0], this review contains the compiler-rt parts of large integer divison for _BitInt.
It adds the functions
```
/// Computes the unsigned division of a / b for two large integers
/// composed of n significant words.
/// Writes the quotient to quo and the remainder to rem.
///
/// \param quo The quotient represented by n words. Must be non-null.
/// \param rem The remainder represented by n words. Must be non-null.
/// \param a The dividend represented by n + 1 words. Must be non-null.
/// \param b The divisor represented by n words. Must be non-null.
/// \note The word order is in host endianness.
/// \note Might modify a and b.
/// \note The storage of 'a' needs to hold n + 1 elements because some
/// implementations need extra scratch space in the most significant word.
/// The value of that word is ignored.
COMPILER_RT_ABI void __udivmodei5(su_int *quo, su_int *rem, su_int *a,
su_int *b, unsigned int n);
/// Computes the signed division of a / b.
/// See __udivmodei5 for details.
COMPILER_RT_ABI void __divmodei5(su_int *quo, su_int *rem, su_int *a, su_int *b,
unsigned int words);
```
into builtins.
In addition it introduces a new "bitint" library containing only those new functions,
which is meant as a way to provide those when using libgcc as runtime.
[0] https://discourse.llvm.org/t/rfc-add-support-for-division-of-large-bitint-builtins-selectiondag-globalisel-clang/60329
Differential Revision: https://reviews.llvm.org/D120327
All platforms return the main executable as the first dl_phdr_info.
FreeBSD, NetBSD, Solaris, and Linux-musl place the executable name
in the dlpi_name field of this entry. It appears that only Linux-glibc
uses the empty string.
To make this work generically on all platforms, unconditionally
skip the first object (like is currently done for FreeBSD and NetBSD).
This fixes first DSO detection on Linux-musl. It also would likely
fix detection on Solaris/Illumos if it were to gain PIE support
(since dlpi_addr would not be NULL).
Additionally, only skip the Linux VDSO on linux.
Finally, use the empty string as the "seen first dl_phdr_info"
marker rather than (char *)-1. If there was no other object, we
would try to dereference it for a string comparison.
Reviewed By: MaskRay, vitalybuka
Differential Revision: https://reviews.llvm.org/D119515
Compiler-rt cross-compile for ARMv5 fails because D99282 made it an error if DMB
is used for any pre-ARMv6 targets. More specifically, the "#error only supported
on ARMv6+" added in D99282 will cause compilation to fail when any source file
which includes assembly.h are compiled for pre-ARMv6 targets. Since the only
place where DMB is used is syn-ops.h (which is only included by
arm/sync_fetch_and_* and these files are excluded from being built for older
targets), this patch moves the definition there to avoid the issues described
above.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D123105
The previous check for interceptors used `pthread_create()` which is not
available on DriverKit. We need an intercepted symbol that satisfies
the following constraints:
- Symbol is available in DriverKit
- Symbol is provided by simulator runtime dylibs (`dlsym()` fails to
look up host-provided symbols)
`puts()` satisfies all of the above constraints.
rdar://87895539
Reviewed By: yln
Differential Revision: https://reviews.llvm.org/D123245
This is useful when building a complete toolchain to ensure that CRT
is built after builtins but before the rest of the compiler-rt.
Differential Revision: https://reviews.llvm.org/D120682
This is useful when building a complete toolchain to ensure that CRT
is built after builtins but before the rest of the compiler-rt.
Differential Revision: https://reviews.llvm.org/D120682
Currently LoadedModule provides max_executable_address.
Replace it with just max_address.
It's only used for printing for human inspection and since
modules are non-overlapping, max_address is as good as max_executable_address
for matching addresses/PCs against modules (I assume it's used for that).
On the hand, max_address is more general and can used to match e.g. data addresses.
I want to use it for that purpose in future changes.
Reviewed By: melver
Differential Revision: https://reviews.llvm.org/D122906
Update the hardware CRC32 logic in scudo to support using `-mcrc32`
instead of `-msse4.2`. The CRC32 intrinsics use the former flag
in the newer compiler versions, e.g. in clang since 12fa608af4.
With these versions of clang, passing `-msse4.2` is insufficient
to enable the instructions and causes build failures when `-march` does
not enable CRC32 implicitly:
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-14.0.0/work/compiler-rt/lib/scudo/scudo_crc32.cpp:20:10: error: always_inline function '_mm_crc32_u32' requires target feature 'crc32', but would be inlined into function 'computeHardwareCRC32' that is compiled without support for 'crc32'
return CRC32_INTRINSIC(Crc, Data);
^
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-14.0.0/work/compiler-rt/lib/scudo/scudo_crc32.h:27:27: note: expanded from macro 'CRC32_INTRINSIC'
# define CRC32_INTRINSIC FIRST_32_SECOND_64(_mm_crc32_u32, _mm_crc32_u64)
^
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-14.0.0/work/compiler-rt/lib/scudo/../sanitizer_common/sanitizer_platform.h:132:36: note: expanded from macro 'FIRST_32_SECOND_64'
# define FIRST_32_SECOND_64(a, b) (a)
^
1 error generated.
For backwards compatibility, use `-mcrc32` when available and fall back
to `-msse4.2`. The `<smmintrin.h>` header remains in use as it still
works and is compatible with GCC, while clang's `<crc32intrin.h>`
is not.
Use __builtin_ia32*() rather than _mm_crc32*() when using `-mcrc32`
to preserve compatibility with GCC. _mm_crc32*() are aliases
to __builtin_ia32*() in both compilers but GCC requires `-msse4.2`
for the former, while both use `-mcrc32` for the latter.
Originally reported in https://bugs.gentoo.org/835870.
Differential Revision: https://reviews.llvm.org/D122789
This reverts commit 09b53121c3.
Breaks the build with GCC 11.2 on x86_64:
In file included from /home/npopov/repos/llvm-project/compiler-rt/lib/scudo/scudo_crc32.h:27,
from /home/npopov/repos/llvm-project/compiler-rt/lib/scudo/scudo_crc32.cpp:14:
/usr/lib/gcc/x86_64-redhat-linux/11/include/smmintrin.h: In function ‘__sanitizer::u32 __scudo::computeHardwareCRC32(__sanitizer::u32, __sanitizer::uptr)’:
/usr/lib/gcc/x86_64-redhat-linux/11/include/smmintrin.h:846:1: error: inlining failed in call to ‘always_inline’ ‘long long unsigned int _mm_crc32_u64(long long unsigned int, long long unsigned int)’: target specific option mismatch
846 | _mm_crc32_u64 (unsigned long long __C, unsigned long long __V)
On Darwin, we want to limit the parallelism during test execution for
sanitizer tests that use shadow memory. The reason is explained by this
existing comment:
> Only run up to 3 processes that require shadow memory simultaneously
> on 64-bit Darwin. Using more scales badly and hogs the system due to
> inefficient handling of large mmap'd regions (terabytes) by the
> kernel.
Previously we detected 3 cases:
* on-device: limit to 1 process
* 64-bit: macOS & simulators, limit to 3 processes
* others (32-bit): no limitation
We checked for the 64-bit case like this: `if arch in ['x86_64',
'x86_64h']` which misses macOS running on AS. Additionally, we don't
care about 32-bit anymore, so I've simplified this to 2 cases: on-device
and everything else.
Differential Revision: https://reviews.llvm.org/D122751
Update the hardware CRC32 logic in scudo to support using `-mcrc32`
instead of `-msse4.2`. The CRC32 intrinsics use the former flag
in the newer compiler versions, e.g. in clang since 12fa608af4.
With these compilers, passing `-msse4.2` is insufficient to enable
the instructions and causes build failures when `-march` does not enable
CRC32:
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-14.0.0/work/compiler-rt/lib/scudo/scudo_crc32.cpp:20:10: error: always_inline function '_mm_crc32_u32' requires target feature 'crc32', but would be inlined into function 'computeHardwareCRC32' that is compiled without support for 'crc32'
return CRC32_INTRINSIC(Crc, Data);
^
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-14.0.0/work/compiler-rt/lib/scudo/scudo_crc32.h:27:27: note: expanded from macro 'CRC32_INTRINSIC'
# define CRC32_INTRINSIC FIRST_32_SECOND_64(_mm_crc32_u32, _mm_crc32_u64)
^
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-14.0.0/work/compiler-rt/lib/scudo/../sanitizer_common/sanitizer_platform.h:132:36: note: expanded from macro 'FIRST_32_SECOND_64'
# define FIRST_32_SECOND_64(a, b) (a)
^
1 error generated.
For backwards compatibility, use `-mcrc32` when available and fall back
to `-msse4.2`. The `<smmintrin.h>` header remains in use as it still
works and is compatible with GCC, while clang's `<crc32intrin.h>`
is not.
Originally reported in https://bugs.gentoo.org/835870.
Differential Revision: https://reviews.llvm.org/D122789
dd9173420f (Add clear_cache implementation for ppc64. Fix buffer to
meet ppc64 alignment., 2017-07-28), adds an implementation for
__builtin___clear_cache on powerpc64, which was promptly ammended to
also be used with big endian mode in f67036b62c (This ppc64 implementation
of clear_cache works for both big and little endian., 2017-08-02)
clang will use this implementation for it's builtin on FreeBSD and result
in an abort() in the cases where 32-bit generation was requested (ex in
macppc or when the big endian powerpc64 build was done with "-m32") and as
reported[1] recently with pcre2, but there is no reason why the same code
couldn't be used in those cases, so use instead the more generic identifier
for the PowerPC architecture.
While at it, update the comment to reflect that POWER8/9 have a 128 byte
wide cache line and so the code could instead use 64 byte windows instead
but that possible optimization has been punted for now.
[1] https://github.com/PhilipHazel/pcre2/issues/92
Reviewed By: jhibbits, #powerpc, MaskRay
Differential Revision: https://reviews.llvm.org/D122640
* Support compiling with clang-5
* Check for `LLVM_DISABLE_ASSEMBLY_FILES` and have it set by
`compiler-rt/lib/sanitizer_common/symbolizer/scripts/build_symbolizer.sh`
which wants to receive and process only bitcode files.
This is a re-land of https://reviews.llvm.org/D86171 with fix.
Fuchsia's system libraries are instrumented and use the lsan
allocator for internal purposes. So leak checking needs to run
after all atexit hooks and after the system libraries' internal
exit-time hooks. The <zircon/sanitizer.h> hook API calls the
__sanitizer_process_exit_hook function at exactly the right time.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D88248
Add include to resolve compiler warning about no previous extern declaration for non-static HashAlgorithm
Differential Revision: https://reviews.llvm.org/D122630
Compiler warns about HeaderPos possibly being uninitialized which should not be possible, but just initialize it anyway
Differential Revision: https://reviews.llvm.org/D122632
Use Fuchsia's zx_system_get_features API to determine
whether LSE atomics are available on the machine.
Reviewed By: abrachet
Differential Revision: https://reviews.llvm.org/D118839
This has never really been used in practice. Fuchsia is moving
away from the support this requires, so don't use it.
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D122500
After landing D121813 the binary size increase introduced by this change can be minimized by using --gc-sections link options. D121813 allows each individual callbacks to be optimized out if not used.
Reviewed By: vitalybuka, MaskRay
Differential Revision: https://reviews.llvm.org/D122407
Currently, we only print how threads involved in data race are created from their parent threads.
Add a runtime flag 'print_full_thread_history' to print thread creation stacks for the threads involved in the data race and their ancestors up to the main thread.
Reviewed By: dvyukov
Differential Revision: https://reviews.llvm.org/D122131
This patch updates the existing default no-arg constructor for
MemInfoBlock to explicitly initialize all members. Also add missing
DataTypeId initialization to the other constructor. These issues were
exposed by msan on patch D121179. With this patch D121179 builds cleanly
on msan.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D122260
For errno spoiling reports we only print the stack
where the signal handler is invoked. And the top
frame is the signal handler function, which is supposed
to give the info for debugging.
But in same cases the top frame can be some common thunk,
which does not give much info. E.g. for Go/cgo it's always
runtime.cgoSigtramp.
Print the signal number.
This is what we can easily gather and it may give at least
some hints regarding the issue.
Reviewed By: melver, vitalybuka
Differential Revision: https://reviews.llvm.org/D121979
Explicitly specify the class name to avoid selecting the wrong Run function, and inherit from the correct Test parent
Differential Revision: https://reviews.llvm.org/D121854
Tests can register multiple allocators, but only the first will initialize since it initializes the TSDRegistrySharedT. Then, destruction of subsequent allocator may end up unmapping a nullptr PrimaryBase with non-zero PrimarySize.
Differential Revision: https://reviews.llvm.org/D121858
-fsanitize-memory-use-after-dtor detects memory access after a
subobject is destroyed but its memory is not yet deallocated.
This is done by poisoning each object memory near the end of its destructor.
Subobjects (members and base classes) do this in their respective
destructors, and the parent class does the same for its members with
trivial destructors.
Inexplicably, base classes with trivial destructors are not handled at
all. This change fixes this oversight by adding the base class poisoning logic
to the parent class destructor.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D119300
After e5822ded56, the call to LargeFunction can be optimized out, as x
is never accessed in main. This is causing the test to fail, because the
out-of-bounds access won't be executed.
Adding an extra read and returning the value should prevent the
optimizer from removing the call.
glibc >= 2.33 uses shared functions for stat family functions.
D111984 added support for non-64 bit variants but they
do not appear to be enough as we have been noticing msan
errors on 64-bit stat variants on Chrome OS.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D121652
If sanitizer cannot determine name of the module it
will use "<unknown module>". Then it can be suppressed
if needed.
Reviewed By: kda
Differential Revision: https://reviews.llvm.org/D121674
Fix darwin interface test after D121464. asan_rtl_x86_64.S is not
available on Darwin.
Reviewed By: kstoimenov
Differential Revision: https://reviews.llvm.org/D121636
For ppc64 PIE, it seems that [0xa00000000000,0xc00000000000) may be occupied
which will lead to a segfault in certain kernel configurations
(clang-ppc64le-rhel). Use the `!kUsingConstantSpaceBeg` code path like Fuchsia.
Reviewed By: jsji
Differential Revision: https://reviews.llvm.org/D121257
.thumb_func was not switching mode until [1]
so it did not show up but now that .thumb_func (without argument) is
switching mode, its causing build failures on armv6 ( rpi0 ) even when
build is explicitly asking for this file to be built with -marm (ARM
mode), therefore use DEFINE_COMPILERRT_FUNCTION macro to add function
header which considers arch and mode from compiler cmdline to decide if
the function is built using thumb mode or arm mode.
[1] https://reviews.llvm.org/D101975
Note that it also needs https://reviews.llvm.org/D99282
Reviewed By: peter.smith, MaskRay
Differential Revision: https://reviews.llvm.org/D104183
This clarifies that this is an LLVM specific variable and avoids
potential conflicts with other projects.
Differential Revision: https://reviews.llvm.org/D119918
This is a part of optimized callback reverts. This is needed to export the callbacks from the rt-asan libraries.
Reviewed By: kstoimenov
Differential Revision: https://reviews.llvm.org/D121464
At present compiler-rt cross compiles for armv6 ( -march=armv6 ) but includes
dmb instructions which are only available in armv7+ this causes SIGILL on
clang+compiler-rt compiled components on rpi0w platforms.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D99282
The false positive fixed by commit f831d6fc80
("tsan: fix false positive during fd close") still happens episodically
on the added more stressful test which does just open/close.
I don't have a coherent explanation as to what exactly happens
but the fix fixes the false positive on this test as well.
The issue may be related to lost writes during asynchronous MADV_DONTNEED.
I've debugged similar unexplainable false positive related to freed and
reused memory and at the time the only possible explanation I found is that
an asynchronous MADV_DONTNEED may lead to lost writes. That's why commit
302ec7b9bc ("tsan: add memory_limit_mb flag") added StopTheWorld around
the memory flush, but unfortunately the commit does not capture these findings.
Reviewed By: melver
Differential Revision: https://reviews.llvm.org/D121363
Use the correct types for OFF_T, __sanitizer_time_t and
__sanitizer_dirent and forward time_t related functions
to fix using compiler-rt with 32-bit musl libc.
Also redirect the time_t functions that are affected by
https://musl.libc.org/time64.html to use their 64-bit
ABI names.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D119358
follow up to 0a4dec6cc2.
add unsupported for s390 (SEGV)
restore line that s390 complains, so following asserts work.
Differential Revision: https://reviews.llvm.org/D121326
FdClose is a subjet to the same atomicity problem as MemoryRangeFreed
(memory state is not "monotoic" wrt race detection).
So we need to lock the thread slot in FdClose the same way we do
in MemoryRangeFreed.
This fixes the modified stress.cpp test.
Reviewed By: vitalybuka, melver
Differential Revision: https://reviews.llvm.org/D121143
This is useful when building a complete toolchain to ensure that CRT
is built after builtins but before the rest of the compiler-rt.
Differential Revision: https://reviews.llvm.org/D120682
This fixes a warning about comparing mismatched types. Since `mmap()` already returns a `void *` use that as the pointer type for comparison.
Reviewed By: kyulee, zequanwu
Differential Revision: https://reviews.llvm.org/D120945
Pass LIBCXX_HAS_PTHREAD_LIB, LIBCXX_HAS_RT_LIB and LIBCXXABI_HAS_PTHREAD_LIB
through to the custom lib++ builds so that libfuzzer doesn't end up with a .deplibs section that
links against those libraries when the variables are set to false.
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D120946
The upstream project ships CMake rules for building vanilla gtest/gmock which conflict with the names chosen by LLVM. Since LLVM's build rules here are quite specific to LLVM, prefixing them to avoid collision is the right thing (i.e. there does not appear to be a path to letting someone *replace* LLVM's googletest with one they bring, so co-existence should be the goal).
This allows LLVM to be included with testing enabled within projects that themselves have a dependency on an official gtest release.
Reviewed By: mehdi_amini
Differential Revision: https://reviews.llvm.org/D120789
Aaron Ballman