Extend compiler version detection with clang

[gemesa]

Previously when compiled with clang the version check returned this misleading gcc version:

$ ./hcxdumptool -v
hcxdumptool 6.3.2 (C) 2023 ZeroBeat
...
compiled by gcc 4.2.1
...

I guess it is because clang defines the __GNUC__ macros for some compatibility reasons or something like that.

I think clang is becoming more widespread so this case should be handled. Now, after the changes the version check is fixed:

$ make CC=clang                                                  
fatal: No names found, cannot describe anything.
clang -O3 -Wall -Wextra -Wpedantic -std=gnu99   -o hcxdumptool hcxdumptool.c -DVERSION_TAG=\"6.3.2\" -DVERSION_YEAR=\"2023\" -DHCXSTATUSOUT -DHCXNMEAOUT
$ ./hcxdumptool -v
...
compiled by clang 17.0.6
...
$ make clean
...
$ make
fatal: No names found, cannot describe anything.
cc -O3 -Wall -Wextra -Wpedantic -std=gnu99   -o hcxdumptool hcxdumptool.c -DVERSION_TAG=\"6.3.2\" -DVERSION_YEAR=\"2023\" -DHCXSTATUSOUT -DHCXNMEAOUT
$ ./hcxdumptool -v
...
compiled by gcc 13.2.1
..

[ZerBea]

Thanks, merged but modified because gcc should be on first rank.

[gemesa]

That would have been my preference also but with this approach we are back to the original problem because __GNUC__ is defined both by gcc and clang so the branch #elif defined(__clang__) is never hit. If you want to check for __GNUC__ first, you could write something like this:

#if defined(__GNUC__) && !defined(__clang__)
fprintf(stdout, "compiled by gcc %d.%d.%d\n", __GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__);
#elif defined(__clang__)
fprintf(stdout, "compiled by clang %d.%d.%d\n", __clang_major__, __clang_minor__, __clang_patchlevel__);
...

[ZerBea]

Thanks, that is better:

$ ./hcxdumptool -v
hcxdumptool 6.3.2-145-g4fd4dfb (C) 2023 ZeroBeat
running on Linux kernel 6.6.7-arch1-1
running GNU libc version 2.38
compiled by gcc 13.2.1
compiled with Linux API headers 6.4.0
compiled with GNU libc headers 2.38
enabled REALTIME DISPLAY
enabled GPS support
enabled BPF compiler

$ ./hcxdumptool -v
hcxdumptool 6.3.2-145-g4fd4dfb (C) 2023 ZeroBeat
running on Linux kernel 6.6.7-arch1-1
running GNU libc version 2.38
compiled by clang 16.0.6
compiled with Linux API headers 6.4.0
compiled with GNU libc headers 2.38
enabled REALTIME DISPLAY
enabled GPS support
enabled BPF compiler