https://bugs.llvm.org/show_bug.cgi?id=39410
Bug ID: 39410
Summary: [IA] clang hangs with `-no-integrated-as -Wa,-`
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: libclang
Assignee: unassignedclangb...@nondot.org
Reporter: ndesaulni...@google.com
CC: echri...@gmail.com, kli...@google.com,
lloz...@chromium.org, llvm-bugs@lists.llvm.org,
natechancel...@gmail.com, srhi...@google.com
>From https://lkml.org/lkml/2018/10/23/136.
The linux kernel as of 4.20 for x86_64 uses the flag `-Wa,-` with `-pipe`.
This causes the use of `no-integrated-as` to hang the build. I *think* `-pipe`
is a red herring.
ie.
$ clang hello_world.c -no-integrated-as -Wa,-
can reproduce the issue. strace'ing with and without -Wa,-, I see:
with -Wa,-:
...
access("/usr/bin/as", F_OK) = 0
...
wait4(167173,
w/o: -Wa,-:
access("/usr/bin/as", F_OK) = 0
...
wait4(167996, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 167996
...
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=167996,
si_uid=366559, si_status=0, si_utime=0, si_stime=1} ---
so however clang is invoking the non-integrated-as, it's not receiving SIGCHLD
in order to exit the `wait4`.
Looking at
$ strace gcc hello_world.c -Wa,-
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