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[sr #110484] CFLAGS/CXXFLAGS and CPPFLAGS order in c.m4 ac_compile is no
From: |
anonymous |
Subject: |
[sr #110484] CFLAGS/CXXFLAGS and CPPFLAGS order in c.m4 ac_compile is nonstandard |
Date: |
Wed, 5 May 2021 11:10:44 -0400 (EDT) |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Firefox/78.0 |
URL:
<https://savannah.gnu.org/support/?110484>
Summary: CFLAGS/CXXFLAGS and CPPFLAGS order in c.m4
ac_compile is nonstandard
Project: Autoconf
Submitted by: None
Submitted on: Wed 05 May 2021 03:10:42 PM UTC
Category: None
Priority: 5 - Normal
Severity: 4 - Important
Status: None
Privacy: Public
Assigned to: None
Originator Email: dev@jpoiret.xyz
Open/Closed: Open
Discussion Lock: Any
Operating System: None
_______________________________________________________
Details:
The definition of ac_compile in lib/autoconf/c.m4 contains
$CFLAGS/$CXXFLAGS/$OBJCFLAGS before $CPPFLAGS, whereas the usual expected
order (for example in the implicit rules of GNU automake) is the other way
around. This prevents other macros from working as expected when flag
shadowing is involved.
One such case is AX_CHECK_COMPILE_FLAG of autoconf-archive being unable to
properly detect accepted compiler flags: it appends the tested flag to
C/CXXFLAGS and tries to compile with AC_COMPILE_IFELSE, but a flag set in
CPPFLAGS is able to take precedence, falsifying the result.
A minimal working example is attached, using the latest AX_CHECK_COMPILE_FLAG,
where running
autoconf
./configure CPPFLAGS=-march=native
gives
checking whether C compiler accepts "-march=pentiumpro"... yes
whereas running without CPPFLAGS gives
checking whether C compiler accepts "-march=pentiumpro"... no
This leads to projects which use AX_CC_MAXOPT being unable to compile when
CPPFLAG=-march=native is set.
_______________________________________________________
File Attachments:
-------------------------------------------------------
Date: Wed 05 May 2021 03:10:42 PM UTC Name: configure.ac Size: 2KiB By:
None
<http://savannah.gnu.org/support/download.php?file_id=51384>
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