Description of problem: In GCC 12, Certain Ada source files trigger what looks like infinite tail recursion in add_sibling_attributes in dwarf2out.c. This does not happen in GCC 11. It seems to be specific to 64-bit arches. I don't have a minimal reproducer yet. When building GPRbuild, the problem is triggered by gprbind.adb and gpr-knowledge.adb. Here's an example of a GCC invocation from the package build: /usr/bin/gcc -c -x ada -gnatA -gnat12 -gnaty -gnatQ -gnata -g -gnata -gnatVa -gnatwaCJI -gnatwe -gnatyg -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -gnatn -gnat-p -gnatVd -gnatwn -gnatyN -gnatec=/tmp/GNAT-TEMP-000010.TMP -gnatec=/home/fedora/rombobeorn/rpmbuild/BUILD/gprbuild-2020-20200429-19BD2-src/gpr/debug.adc -gnatem=/tmp/GNAT-TEMP-000011.TMP /home/fedora/rombobeorn/rpmbuild/BUILD/gprbuild-2020-20200429-19BD2-src/gpr/src/gpr-knowledge.adb Version-Release number of selected component (if applicable): 12.0.0-0.5.fc36 How reproducible: It seems deterministic. The problem is triggered by the same two source files every time on x86-64. Builds on aarch64, ppc64le and s390x also get stuck but I don't know the details. The problem does not seem to occur on i686 or armv7hl. Steps to Reproduce: 1. Rebuild the gprbuild package in Rawhide. If _smp_build_ncpus <= 2, then the whole build gets stuck when two gnat1 processes are looping. Otherwise compilation in parallel continues until all the other source files are done and only the two looping processes remain. 2. Run gdb -p with the PID of one of the looping gnat1 processes.
This bug appears to have been reported against 'rawhide' during the Fedora 36 development cycle. Changing version to 36.
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