Files
clang-p2996/compiler-rt/lib/profile/InstrProfilingVersionVar.c
Pirama Arumuga Nainar 69708477be [compiler-rt/profile] Hide __llvm_profile_raw_version
Hide __llvm_profile_raw_version so as not to resolve reference from a
dependent shared object.  Since libclang_rt.profile is added later in
the command line, a definition of __llvm_profile_raw_version is not
included if it is provided from an earlier object, e.g.  from a shared
dependency.

This causes an extra dependence edge where if libA.so depends on libB.so
and both are coverage-instrumented, libA.so uses libB.so's definition of
__llvm_profile_raw_version.  This leads to a runtime link failure if the
libB.so available at runtime does not provide this symbol (but provides
the other dependent symbols).  Such a scenario can occur in Android's
mainline modules.
E.g.:
  ld -o libB.so libclang_rt.profile-x86_64.a
  ld -o libA.so -l B libclang_rt.profile-x86_64.a

libB.so has a global definition of __llvm_profile_raw_version.  libA.so
uses libB.so's definition of __llvm_profile_raw_version.  At runtime,
libB.so may not be coverage-instrumented (i.e. not export
__llvm_profile_raw_version) so runtime linking of libA.so will fail.

Marking this symbol as hidden forces each binary to use the definition
of __llvm_profile_raw_version from libclang_rt.profile.

Differential Revision: https://reviews.llvm.org/D111759
2021-10-15 11:56:16 -07:00

19 lines
755 B
C

/*===- InstrProfilingVersionVar.c - profile version variable setup -------===*\
|*
|* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|* See https://llvm.org/LICENSE.txt for license information.
|* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|*
\*===----------------------------------------------------------------------===*/
#include "InstrProfiling.h"
/* uint64 __llvm_profile_raw_version
*
* The runtime should only provide its own definition of this symbol when the
* user has not specified one. Set this up by moving the runtime's copy of this
* symbol to an object file within the archive.
*/
COMPILER_RT_VISIBILITY COMPILER_RT_WEAK uint64_t INSTR_PROF_RAW_VERSION_VAR =
INSTR_PROF_RAW_VERSION;