https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90034
Bug ID: 90034 Summary: gcc hangs on wait4 after vfork after opening tmp file Product: gcc Version: 8.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: todd.freed at gmail dot com Target Milestone: --- Created attachment 46123 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46123&action=edit causes the hang Here is the command: > dd if=bug_input.c bs=1 count=3051 2>/dev/null | gcc -xc - # hangs The hang seems to be specific to this input somehow. If I pass any count < 3051, it does not hang. For any count >= 3051, it hangs. If I pass an offset of any kind, it does not hang. If I take those 3050 bytes and put them in a file instead of passing then to stdin via pipe, it still hangs. > gcc -bug_input_0_3050.c # hangs I've attached the entire file anyway, for context. The file was generated by GNU bison. ----------------------------------- strace snippet from the hang . . . getpid() = 16236 openat(AT_FDCWD, "/tmp/ccPYKe6J.s", O_RDWR|O_CREAT|O_EXCL, 0600) = 3 close(3) = 0 stat("/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.1/cc1", {st_mode=S_IFREG|0755, st_size=26001000, ...}) = 0 access("/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.1/cc1", X_OK) = 0 vfork() = 16237 wait4(16237, ----------------------------------- strace snippet from a non-hang . . . getpid() = 16578 openat(AT_FDCWD, "/tmp/ccBrWed1.s", O_RDWR|O_CREAT|O_EXCL, 0600) = 3 close(3) = 0 stat("/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.1/cc1", {st_mode=S_IFREG|0755, st_size=26001000, ...}) = 0 access("/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.1/cc1", X_OK) = 0 vfork() = 16579 wait4(16579, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 16579 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=16579, si_uid=1000, si_status=0, si_utime=0, si_stime=0} --- getpid() = 16578 openat(AT_FDCWD, "/tmp/ccXHF56n.o", O_RDWR|O_CREAT|O_EXCL, 0600) = 3 close(3) = 0 . . . ----------------------------------- Version Info: todd@euclid ~/bison 0 master % uname -a Linux euclid 5.0.4-arch1-1-ARCH #1 SMP PREEMPT Sat Mar 23 21:00:33 UTC 2019 x86_64 GNU/Linux todd@euclid ~/bison 0 master % pacman -Q gcc gcc 8.2.1+20181127-1 todd@euclid ~/bison 0 master % gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.1/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/ --enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared --enable-threads=posix --enable-libmpx --with-system-zlib --with-isl --enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object --enable-linker-build-id --enable-lto --enable-plugin --enable-install-libiberty --with-linker-hash-style=gnu --enable-gnu-indirect-function --enable-multilib --disable-werror --enable-checking=release --enable-default-pie --enable-default-ssp --enable-cet=auto Thread model: posix gcc version 8.2.1 20181127 (GCC) NOTE : This also repro's on another of my dev machines, with gcc version 8.2.1 20180831 (GCC)