https://sourceware.org/bugzilla/show_bug.cgi?id=28893
Bug ID: 28893
Summary: binutils-2.37: PGO build with Clang results in
configure error: AR with --plugin and rc is required
for LTO build
Product: binutils
Version: 2.37
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: binutils
Assignee: unassigned at sourceware dot org
Reporter: telans at posteo dot de
Target Milestone: ---
Created attachment 13978
--> https://sourceware.org/bugzilla/attachment.cgi?id=13978&action=edit
build.log
Downstream Gentoo report: https://bugs.gentoo.org/833371
It appears that --enable-pgo-build requires checking for GCC plugin support
from within config/gcc-plugin.m4. This breaks the build when CC=clang with the
following:
configure: error: AR with --plugin and rc is required for LTO build
I believe this issue comes from binutils requesting a GCC LTO plugin regardless
of whether Clang is used or not:
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=config/gcc-plugin.m4#l139
>From the above:
136 plugin_names="liblto_plugin.so liblto_plugin-0.dll cyglto_plugin-0.dll"
137 plugin_option=
138 for plugin in $plugin_names; do
139 plugin_so=`${CC} ${CFLAGS} --print-prog-name $plugin`
140 if test x$plugin_so = x$plugin; then
141 plugin_so=`${CC} ${CFLAGS} --print-file-name $plugin`
142 fi
143 if test x$plugin_so != x$plugin; then
144 plugin_option="--plugin $plugin_so"
145 break
146 fi
147 done
When GCC is used as $CC in the two commands, the outputs are:
telans@desktop ~ $ gcc --print-prog-name liblto_plugin.so
/usr/libexec/gcc/x86_64-pc-linux-gnu/11.2.1/liblto_plugin.so
telans@desktop ~ $ gcc --print-file-name liblto_plugin.so
liblto_plugin.so
Compared to Clang:
telans@desktop ~ $ clang --print-prog-name liblto_plugin.so
liblto_plugin.so
telans@desktop ~ $ clang --print-file-name liblto_plugin.so
liblto_plugin.so
As on line 143, test is expecting a difference between the outputs which does
not occur using Clang (it might be testing for the existence of the plugin?).
I'm fairly sure these config tests can be skipped when using Clang + lld, but
I'm not sure. Thanks.
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