https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109805
Bug ID: 109805
Summary: LTO affecting -fdebug-prefix-map
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: sergiodj at sergiodj dot net
Target Milestone: ---
Hi,
In Ubuntu we use -fdebug-prefix-map to remap a package's build directory (which
contains random stuff) into a predictable path under /usr/src. This is done in
order to help debuginfod index the source code for our packages.
Things work very well, but I found a weird corner case involving LTO. The
affected package is vim. You can see the build logs for it here:
https://launchpadlibrarian.net/665520301/buildlog_ubuntu-mantic-amd64.vim_2%3A9.0.1378-2ubuntu1_BUILDING.txt.gz
As you can notice, we're using -fdebug-prefix-map and LTO for the build.
The problem is that the resulting debuginfo doesn't have the remaped directory.
I can replicate the issue locally, and at first I thought this was either bug
#108464 or #87726, but after some digging I'm convinced it's something else.
I've compiled gcc (GCC) 14.0.0 20230510 from the master branch
(608e7f3ab47fe746279c552c3574147aa3d8ee76), and I still can reproduce the
problem.
A simple reproducer for the problem follows:
$ echo 'int main(){}' > foo.c $ ~/gcc/install/bin/gcc -c foo.c -O2 -g
-flto=auto -ffat-lto-objects -fdebug-prefix-map=`pwd`=/aaaaaaa -o foo $
~/gcc/install/bin/gcc foo -flto=auto -ffat-lto-objects -o bar
A workaround for this bug is to either stop using LTO or explicitly set
-fdebug-prefix-map when linking the object.
