[sr #110451] autoconf 2.71 generated configure file does not enable C compiler flag for C99 on Solaris 10

URL:
  <https://savannah.gnu.org/support/?110451>

                 Summary: autoconf 2.71 generated configure file does not
enable C compiler flag for C99 on Solaris 10
                 Project: Autoconf
            Submitted by: haible
            Submitted on: Sat 27 Feb 2021 09:05:03 PM CET
                Category: None
                Priority: 5 - Normal
                Severity: 3 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
        Operating System: Solaris

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Details:

This is a regression in autoconf 2.71, compared to autoconf 2.69.

Find attached two tarballs, hello-c-2.69.tar.gz (generated with autoconf 2.69)
and hello-c-2.71.tar.gz (generated with autoconf 2.71). They contain the same
source code, except for the version number in configure.ac. In particular,
they contain
  - in configure.ac, an AC_PROG_CC_C99 invocation,
  - in hello.c: code that requires C99.

The commands to regenerate everything in these tarballs is:

aclocal -I m4
autoconf
autoheader
automake -a -c
rm -rf autom4te.cache


On Solaris 10, I'm using CC="cc -O". This compiler is not C99 compliant, but
it accepts the option '-xc99' which makes it C99 compliant.

Both packages ought to exhibit the same behaviour, but they don't:

* The hello-c-2.69 package compiles fine.
  ./configure prints:

checking whether we are using the GNU C compiler... no
checking whether cc -O accepts -g... yes
checking for cc -O option to accept ISO C89... none needed
checking whether cc -O understands -c and -o together... yes
checking whether make supports the include directive... yes (GNU style)
checking dependency style of cc -O... none
checking for cc -O option to accept ISO C99... -D_STDC_C99=

The option '-D_STDC_C99=' is probably not entirely equivalent to '-xc99', but
it is good enough: The compilation command

cc -O -D_STDC_C99= -DHAVE_CONFIG_H -I. -I..  -g -c -o hello.o ../hello.c

succeeds.

* The hello-c-2.71 package does not build.
  ./configure prints:

checking whether the compiler supports GNU C... no
checking whether cc -O accepts -g... yes
checking for cc -O option to enable C11 features... unsupported
checking for cc -O option to enable C99 features... unsupported
checking for cc -O option to enable C89 features... none needed

Then the compilation command fails:

cc -O -DHAVE_CONFIG_H -I. -I..  -g -c -o hello.o ../hello.c
"/usr/include/sys/feature_tests.h", line 341: #error: "Compiler or options
invalid; UNIX 03 and POSIX.1-2001 applications       require the use of c99"
cc: acomp failed for ../hello.c
*** Error code 2


When I set CC="cc -O -xc99", then ./configure prints

checking whether the compiler supports GNU C... no
checking whether cc -O -xc99 accepts -g... yes
checking for cc -O -xc99 option to enable C11 features... unsupported
checking for cc -O -xc99 option to enable C99 features... none needed

and the compilation command succeeds:

cc -O -xc99 -DHAVE_CONFIG_H -I. -I..     -g -c -o hello.o ../hello.c


So, that is a workaround. But the point of the AC_PROG_CC_C99 macro is that
the autoconfiguration finds out about the '-xc99' by itself, isn't it?




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File Attachments:


-------------------------------------------------------
Date: Sat 27 Feb 2021 09:05:03 PM CET  Name: hello-c-2.69.tar.gz  Size: 75KiB 
 By: haible

<http://savannah.gnu.org/support/download.php?file_id=50939>
-------------------------------------------------------
Date: Sat 27 Feb 2021 09:05:03 PM CET  Name: hello-c-2.71.tar.gz  Size: 75KiB 
 By: haible

<http://savannah.gnu.org/support/download.php?file_id=50940>

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