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GCC 5.1 is too smart. Disable Identical Code Folding for preload libs.

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We want to disabled Identical Code Folding for the tools preload shared
objects to get better backraces. For GCC 5.1 -fipa-icf is enabled by
default at -O2.

    The optimization reduces code size and may disturb
    unwind stacks by replacing a function by equivalent
    one with a different name.

Add a configure check to see if GCC supports -fno-ipa-icf.
If it does then add the flag to AM_CFLAGS_PSO_BASE.

Without this GCC will notice some of the preload replacement functions
in vg_replace_strmem are identical and fold them all into one picking
a random (existing) function name. This causes backtraces showing
completely unexpected function names.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15305
This commit is contained in:
Mark Wielaard 2015-06-02 20:23:06 +00:00
parent 9c0019f28a
commit d2b96ae95b
2 changed files with 29 additions and 2 deletions
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4
Makefile.all.am
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@ -133,10 +133,10 @@ endif
if VGCONF_OS_IS_DARWIN
AM_CFLAGS_PSO_BASE = -dynamic \
-O -g -fno-omit-frame-pointer -fno-strict-aliasing \
-fpic -fPIC -fno-builtin
-fpic -fPIC -fno-builtin @FLAG_FNO_IPA_ICF@
else
AM_CFLAGS_PSO_BASE = -O -g -fno-omit-frame-pointer -fno-strict-aliasing \
-fpic -fno-builtin
-fpic -fno-builtin @FLAG_FNO_IPA_ICF@
endif

27
configure.ac
View File

@ -1811,6 +1811,33 @@ CFLAGS=$safe_CFLAGS
AC_SUBST(FLAG_FNO_STACK_PROTECTOR)
# Does GCC support disabling Identical Code Folding?
# We want to disabled Identical Code Folding for the
# tools preload shared objects to get better backraces.
# For GCC 5.1+ -fipa-icf is enabled by default at -O2.
# "The optimization reduces code size and may disturb
# unwind stacks by replacing a function by equivalent
# one with a different name."
AC_MSG_CHECKING([if gcc accepts -fno-ipa-icf])
safe_CFLAGS=$CFLAGS
CFLAGS="-fno-ipa-icf"
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[
return 0;
]])], [
no_ipa_icf=yes
FLAG_FNO_IPA_ICF="-fno-ipa-icf"
AC_MSG_RESULT([yes])
], [
no_ipa_icf=no
FLAG_FNO_IPA_ICF=""
AC_MSG_RESULT([no])
])
CFLAGS=$safe_CFLAGS
AC_SUBST(FLAG_FNO_IPA_ICF)
# Does this compiler support -fsanitize=undefined?
# Only checked for if --enable-ubsan was given.