From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
To: Robin Templeton <robin@igalia.com>
Cc: 32767-done@debbugs.gnu.org
Subject: bug#32767: glibc shadows gcc's C++ headers
Date: Tue, 09 Mar 2021 16:35:19 -0500 [thread overview]
Message-ID: <87h7lkui20.fsf@gmail.com> (raw)
In-Reply-To: <87efdquy26.fsf@terpri.org> (Robin Templeton's message of "Tue, 18 Sep 2018 20:32:17 -0400")
Hello,
Robin Templeton <robin@igalia.com> writes:
> When compiling C++ programs, glibc's include directory takes precedence
> over gcc's for standard C headers like math.h, but glibc's headers
> aren't completely compatible with C++. For example, isnan from math.h is
> supposed to be a function, but glibc defines it as a macro.
>
> This program demonstrates the problem:
>
> #include <math.h>
> int main(void) { int isnan(0); return isnan; }
>
> It works as expected when gcc's built-in C++ headers are used, but not
> if glibc is installed:
>
> % guix environment --pure --ad-hoc gcc -- g++ -E isnan.cpp | tail -n1
> int main (void) { int isnan (0); return isnan; }
> % guix environment --pure --ad-hoc gcc glibc -- g++ -E isnan.cpp | tail -n1
> int main (void) { int __builtin_isnan (0); return isnan; }
>
> As a temporary workaround, I'm using the following package as a
> replacement for glibc, to keep the glibc headers out of $CPATH. If it's
> installed along with gcc, ld-wrapper and binutils, the test program
> compiles without errors.
>
> (use-modules (guix) (gnu))
> (use-package-modules base)
> (package
> (inherit glibc)
> (name "my-glibc")
> (arguments
> (substitute-keyword-arguments (package-arguments glibc)
> ((#:phases phases)
> `(modify-phases ,phases
> (add-after 'install 'move-include
> (lambda _
> (rename-file (string-append %output "/include")
> (string-append %output "/include-glibc"))
> #t)))))))
Thanks for the report. Nowadays the recommended way to install the
GCC-based toolchain is to use the 'gcc-toolchain' package. The 'gcc'
package is now even made hidden in Guix, which doesn't seem to have this
particular issue:
$ guix environment --pure --ad-hoc gcc-toolchain -- g++ -E /tmp/isnan.cpp | tail -n1
int main(void) { int isnan(0); return isnan; }
$ guix environment --pure --ad-hoc gcc-toolchain glibc -- g++ -E /tmp/isnan.cpp | tail -n1
int main(void) { int isnan(0); return isnan; }
I'm closing this issue, but feel free to open a fresh one if you still
encounter problems.
Thank you,
Maxim
prev parent reply other threads:[~2021-03-09 21:37 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-19 0:32 bug#32767: glibc shadows gcc's C++ headers Robin Templeton
2021-03-09 21:35 ` Maxim Cournoyer [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87h7lkui20.fsf@gmail.com \
--to=maxim.cournoyer@gmail.com \
--cc=32767-done@debbugs.gnu.org \
--cc=robin@igalia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/guix.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.