Build failure with GCC 15: custom_getenv declared with empty parameter list, incompatible with C23

[SamHerts]

Building Spindle with GCC 15 fails in src/utils/parseloc.c when compiling the SLURM plugin

../../src/utils/parseloc.c: In function 'parse_location_impl':
../../src/utils/parseloc.c:106:25: error: too many arguments to function 'custom_getenv'; expected 0, have 1
  106 |             env_value = custom_getenv(envvar);
      |                         ^~~~~~~~~~~~~ ~~~~~~
../../src/utils/parseloc.c:46:14: note: declared here
   46 | extern char *custom_getenv();
      |              ^~~~~~~~~~~~~

Root Cause:

parseloc declares custom_getenv with an empty parameter list:

Spindle/src/utils/parseloc.c

Line 46 in 4174224

extern char *custom_getenv();

while the actual definition in src/slurm_plugin/slurm_plugin has always taken one argument:

Spindle/src/slurm_plugin/slurm_plugin.c

Lines 509 to 512 in 4174224

	char *custom_getenv(char *envname)
	{
	return readSpankEnv(current_spank, envname);
	}

C Reference denotes the empty parameter list is obsolete in c23, GNU Reference calls it bad practice.

Suggested fix

Update the declaration in src/utils/parseloc.c:46 to match the slurm plugin definition:

extern char *custom_getenv(char *envname);

Environment

• Spindle: devel branch (commit 4174224)
• OS: Rocky Linux 10.1 (Red Quartz)
• Compiler: GCC 15 (gnu15 toolchain)
• Affected files: src/utils/parseloc.c:46, src/slurm_plugin/slurm_plugin.c:509