[compiler-rt/profile] Reland mark __llvm_profile_raw_version as hidden

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.  The visiblity
is unchanged for Apple platforms where its presence is checked by the
TAPI tool.

Reviewed By: MaskRay, phosek, davidxl

Differential Revision: https://reviews.llvm.org/D111759

0 files changed, 0 insertions, 0 deletions