[PROJ] Why is std=gnu89 tested/enabled ?

[Markus Metz]

On Wed, Aug 21, 2019 at 2:10 PM Kristian Evers <kreve at sdfe.dk> wrote:
>
> No, I don’t think so. Internally PROJ defines some math functions that is
first introduced with C99. If the build system detects that they are
available with your compiler the system functions are used instead. As far
as I remember that is the only difference between using C89

PROJ used -std=gnu89 which is not the same like -std=c89, because only
gnu89 includes some C99 features which might not be available on Solaris
with -std=gnu89. If PROJ wants to enforce a particular standard, it should
probably use -std=c<xy> instead of -std=gnu<xy>, if PROJ is supposed to
compile on non-GNU (double negation) systems.

my2c

Markus M


> and C99 to build PROJ 5.2.0. Try running the test suite, it should give
you a good indication if it works or not.
>
> /Kristian
>
> On 21 Aug 2019, at 13:55, Dechaux Eric CEN (BCQ STIG) <
eric.dechaux at gendarmerie.interieur.gouv.fr> wrote:
>
> Thanks Kristian,
>
> On Solaris, NAN is not available with C89. Is there an issue to build
proj 5 forcing C99 by replacing -std=c89 to -std=c99 in the Makefile, after
configure ?
>
>
> Regards.
>
>
> Le 21/08/2019 à 12:43, Kristian Evers a écrit :
>
> Eric,
>
> A C++11 compatible compiler is only required for PROJ 6 and onwards. This
was introduced with RFC3 [0]. Previous versions was strictly C89, hence the
enforcement of that standard in PROJ 5.2.0.
>
> /Kristian
>
> [0] https://proj.org/community/rfc/rfc-3.html
>
> On 16 Aug 2019, at 14:57, Dechaux Eric CEN (BCQ STIG) <
eric.dechaux at gendarmerie.interieur.gouv.fr> wrote:
>
> Greetings,
>
> I have been investigating proj 5.2.0 build failure on Solaris 11.3 for
amd64. At some point the build stops on error because of the NAN being not
declared :
>
> gcc -DHAVE_CONFIG_H -I.
-DPROJ_LIB=\"/appli/stig/11.3-20190816-104632/share/proj\" -DMUTEX_pthread
 -D_FORTIFY_SOURCE=2 -I/usr/include/pcre
-I/appli/stig/11.3-20190816-104632/include -Wall
-Wdeclaration-after-statement -Wextra -Winit-self -Wunused-parameter
-Wmissing-prototypes -Wmissing-declarations -Wformat
-Werror=format-security -Wno-format-nonliteral -Wlogical-op -Wshadow
-Werror=vla -Wdeclaration-after-statement -Wdate-time -Wfloat-conversion
-std=gnu89 -m64 -O2 -fstack-protector-strong -fpic -fPIC
--param=ssp-buffer-size=4 -I/appli/stig/11.3-20190816-104632/include
-DHAVE_C99_MATH=1 -MT proj_strtod.o -MD -MP -MF .deps/proj_strtod.Tpo -c -o
proj_strtod.o proj_strtod.c
> gie.c: In function ‘cart_selftest’:
> gie.c:2008:20: error: ‘NAN’ undeclared (first use in this function)
>      a = proj_coord(NAN, NAN, NAN, NAN);
>                     ^
> gie.c:2008:20: note: each undeclared identifier is reported only once for
each function it appears in
> make[2]: *** [gie.o] Erreur 1
>
>
> As the documentation specify a C and C++11 compiler is required I changed
the CFLAGS to include -std=gnu11. The build and checks run without errror.
Solaris 11.3 is bundled with GCC 5.3 with uses gnu11 by default for C and
there should be no reason to force for it on the CFLAGS.
>
> I noticed the configure script detects and automatically adds -std=gnu89
to the CFLAGS :
>
>     checking whether C compiler accepts -Wdocumentation
-Wno-documentation-deprecated-sync... no
>     checking if -std=gnu89 can be enabled... yes
>     checking whether C++ compiler accepts -Wunused-private-field... no
>
>
> On Solaris this disables the NAN macro as it is C99:
>
> $ cat test.c
> #include <stdlib.h>
> #include <math.h>
>
> int main (void) {
>
>         float f ;
>         f = NAN ;
>
>
>         exit (EXIT_SUCCESS) ;
> }
>
> $ gcc -std=gnu89 test.c
> test.c: In function ‘main’:
> test.c:7:6: error: ‘NAN’ undeclared (first use in this function)
>   f = NAN ;
>       ^
> test.c:7:6: note: each undeclared identifier is reported only once for
each function it appears in
>
> $ gcc -std=gnu99 test.c
>
> $ gcc -std=gnu11 test.c
>
>
>
> What is the purpose of forcing C standard to gnu89  ?
>
>
>
> Thanks.
>
> -- Eric
>
>
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