URL:
<https://savannah.gnu.org/support/?110268>
Summary: AC_RUN_IFELSE does not execute the test program
although it could
Project: Autoconf
Submitted by: haible
Submitted on: Wed 15 Jul 2020 09:58:09 AM CEST
Category: None
Priority: 5 - Normal
Severity: 4 - Important
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Operating System: None
_______________________________________________________
Details:
This is a regression, compared to 2.69.
In situations where a platform is used as a development environment - with
program execution capability - for a different platform, AC_RUN_IFELSE now
does not execute the test program although it could; it falls back to the
cross-compilation guess instead.
This affects in particular
1) native Windows (mingw or MSVC) compilation in a Cygwin environment,
2) cross-compilation to Linux with a different architecture, on Linux.
Details about the environments:
1) See
https://git.savannah.gnu.org/gitweb/?p=gettext.git;a=blob;f=INSTALL.windows
2) For example, cross-compilation to Linux/m68k from Linux/x86_64 (Ubuntu
16.04). See
https://git.savannah.gnu.org/gitweb/?p=libffcall.git;a=blob;f=porting-tools/emulation/qemu-m68k.txt
. The configure command I use is:
configure --prefix=/inst-m68k --host=m68k-linux CPPFLAGS="-I/inst-m68k/include
-Wall" LDFLAGS="-L/inst-m68k/lib"
The behaviour of AC_RUN_IFELSE is specified in the Autoconf documentation:
"If cross-compilation mode is enabled (this is the case if either the compiler
being used does not produce executables that run on the system where
@command{configure} is being run, or if the options @code{--build} and
@code{--host} were both specified and their values are different), then the
test program is not run."
This documentation has not changed since 2.69, and it makes perfect sense: it
generally allows to determine actual program behaviour, and it has a way to
disable it (in cases where that's needed).
In my case, the generated executables DO run in the environment, and I did NOT
specify a --build option. Therefore AC_RUN_IFELSE should execute the test
program.
Instead, what I see when configuring a gnulib testdir, generated with
+verbose+
./gnulib-tool --create-testdir --dir=../testdir-posixb --with-c++-tests
--single-configure `./posix-modules`
-verbose-
through
+verbose+
./configure --prefix=/inst-m68k --host=m68k-linux
CPPFLAGS="-I/inst-m68k/include -Wall" LDFLAGS="-L/inst-m68k/lib" -C 2>&1 | tee
log1
-verbose-
for Linux/m68k is that all AC_RUN_IFELSE invocation used the cross-compilation
branch, not the test program:
+verbose+
$ diff testdir-posix/build-m68k/config.cache
testdir-posixb/build-m68k/config.cache |head
16a17
> ac_cv_c_decl_report=${ac_cv_c_decl_report=error}
65c66
< ac_cv_func_chown_works=${ac_cv_func_chown_works=yes}
---
> ac_cv_func_chown_works=${ac_cv_func_chown_works='guessing yes'}
107c108
< ac_cv_func_getgroups_works=${ac_cv_func_getgroups_works=yes}
---
> ac_cv_func_getgroups_works=${ac_cv_func_getgroups_works='guessing yes'}
...
-verbose-
See attached file config.cache.diff.
_______________________________________________________
File Attachments:
-------------------------------------------------------
Date: Wed 15 Jul 2020 09:58:09 AM CEST Name: config.cache.diff Size: 31KiB
By: haible
<http://savannah.gnu.org/support/download.php?file_id=49488>
_______________________________________________________
Reply to this item at:
<https://savannah.gnu.org/support/?110268>
_______________________________________________
Message sent via Savannah
https://savannah.gnu.org/
