https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108328
Bug ID: 108328
Summary: gcc --help -v doesn't work correctly in some
circumstances in gcc>=10
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: driver
Assignee: unassigned at gcc dot gnu.org
Reporter: sagimor6 at gmail dot com
Target Milestone: ---
Created attachment 54210
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54210&action=edit
patch to fix the bug
works:
gcc --help -v 2>/dev/null | grep ffunction-sections
(prints the ffunction-section description)
doesn't work:
gcc -Wl,--some-flag --help -v 2>/dev/null | grep ffunction-sections
(nothing is printed)
I am sure that this behavior is incorrect.
also (but maybe less important):
gcc a.c a.c a.c a.c --help -v 2>/dev/null | grep ffunction-sections
this prints the help 4 times (as many times as there are input files).
I am also sure that this behavior is incorrect.
Some programs depend on --help -v to work, for example python. python checks if
fwrapv is supported with the mechanism. buildroot uses something called
toolchain-wrapper to add default flags to gcc when you call it, if you would
check the bootlin compilers in aarch64 they add -Wl,-z,relro by default. So, if
you were to compile python with a bootlin compiler with gcc>=10 it will not
compile with all the correct flags (no fwrapv).
This is just one example (this is where I noticed the bug).
The bug was introduced in the following commit:
https://github.com/gcc-mirror/gcc/commit/2dcfc8722b6146e479039a2f8994050c772b25e6
(commit 2dcfc8722b6146e479039a2f8994050c772b25e6)
So the bug only exists in gcc>=10, and doesn't in gcc<=9.
I created a patch to revert a small part of this commit (will send to the gcc
patches mailing list as well). I tested the patch.
One of the reasons I am sure this is a bug is because of the comment above the
if statement: "Ensure we only invoke each subprocess once.", so the help should
be printed once and only once.
