[Buildroot] [Bug 15231] New: gcc --help -v doesn't work correctly with gcc>=10 and BR2_RELRO_PARTIAL or BR2_RELRO_FULL

From: bugzilla@busybox.net
To: buildroot@uclibc.org
Subject: [Buildroot] [Bug 15231] New: gcc --help -v doesn't work correctly with gcc>=10 and BR2_RELRO_PARTIAL or BR2_RELRO_FULL
Date: Sat, 07 Jan 2023 17:16:25 +0000	[thread overview]
Message-ID: <bug-15231-163@https.bugs.busybox.net/> (raw)

https://bugs.busybox.net/show_bug.cgi?id=15231

            Bug ID: 15231
           Summary: gcc --help -v doesn't work correctly with gcc>=10 and
                    BR2_RELRO_PARTIAL or BR2_RELRO_FULL
           Product: buildroot
           Version: 2020.11.2
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
          Assignee: unassigned@buildroot.uclibc.org
          Reporter: sagimor6@gmail.com
                CC: buildroot@uclibc.org
  Target Milestone: ---

Created attachment 9451
  --> https://bugs.busybox.net/attachment.cgi?id=9451&action=edit
quick fix

gcc --help -v 2>&1 | grep ffunction-sections

This should display the option with description.
But with buildroot gcc>=10 with RELRO protection configured to Partial or Full,
this doesn't work (doesn't display anything).
So affected buildroots are with versions >=2020.11.2
You can check this with bootlin compilers with buildroot>=2021.11

The cause of this is:

1) from gcc 10, the following doesn't work:
gcc -Wl,--some-flag --help -v 2>&1 | grep ffunction-section

I created a bug report:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108328

2) toolchain-wrapper with BR2_RELRO_PARTIAL or BR2_RELRO_FULL adds -Wl,-z,relro
linker flags which trigger this

now, BR2_RELRO_PARTIAL or BR2_RELRO_FULL are the default since 2021.05.

Moreover, this causes the python and python3 package to compile without the
-fwrapv option, because python detects it using the: gcc --help -v 2>&1 | grep
fwrapv

This is just one example that I stumbled upon, I think this can cause problems
in general, and in other packages that do these kinds of checks.

I attached a quick fix patch (should I send it to the mailing list too?), but
feel free to comment on the gcc bug report I created.

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