[eregon]

Fixes https://github.com/truffleruby/truffleruby/actions/runs/40510552782/job/122211001277#step:1:17
which failed with:

compiling build/shared/util/pm_string.o
src/util/pm_string.c: In function ‘pm_string_mapped_init’:
src/util/pm_string.c:186:17: error: storing the address of local variable
‘source’ in ‘*string.source’ [-Werror=dangling-pointer=]
186 |         *string = (pm_string_t) { .type = PM_STRING_CONSTANT, .source =
source, .length = 0 };
|        
~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/util/pm_string.c:185:23: note: ‘source’ declared here
  185 |         const uint8_t source[] = "";
      |                       ^~~~~~
src/util/pm_string.c:118:36: note: ‘string’ declared here
  118 | pm_string_mapped_init(pm_string_t *string, const char *filepath) {
      |                       ~~~~~~~~~~~~~^~~~~~
src/util/pm_string.c: In function ‘pm_string_file_init’:
src/util/pm_string.c:282:17: error: storing the address of local variable
‘source’ in ‘*string.source’ [-Werror=dangling-pointer=]
282 |         *string = (pm_string_t) { .type = PM_STRING_CONSTANT, .source =
source, .length = 0 };
|        
~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/util/pm_string.c:281:23: note: ‘source’ declared here
  281 |         const uint8_t source[] = "";
      |                       ^~~~~~
src/util/pm_string.c:210:34: note: ‘string’ declared here
  210 | pm_string_file_init(pm_string_t *string, const char *filepath) {
      |                     ~~~~~~~~~~~~~^~~~~~
cc1: all warnings being treated as errors
make: *** [Makefile:53: build/shared/util/pm_string.o] Error 1
<internal:core> core/kernel.rb:613:in 'Kernel#system': command failed
(RuntimeError)
	from extconf.rb:51:in 'block in Object#make'
	from <internal:core> core/dir.rb:363:in 'Dir.chdir'
	from extconf.rb:50:in 'Object#make'
	from extconf.rb:68:in '<main>'

extconf failed, exit code 1

Gem files will remain installed in
/home/runner/.rubies/truffleruby-head/lib/gems/gems/prism-1.4.0 for inspection.

Which was trigger by ubuntu-latest becoming 26.04.

Surprisingly the corresponding job on this repo also uses ubuntu-latest but was run on 24.04:
https://github.com/ruby/ruby-bench/actions/runs/40529770004/job/122279069041#step:1:17

---

prism 1.4.0 fails to compile its native extension on non-CRuby engines with GCC 15, as found on the ubuntu-26.04 runner image that ubuntu-latest is migrating to. On those engines prism's extconf.rb builds libprism via the gem's own Makefile, which uses -Werror, and GCC 15 reports:

src/util/pm_string.c:186:17: error: storing the address of local
variable 'source' in '*string.source' [-Werror=dangling-pointer=]

prism 1.6.0 fixed this by using a static empty_source array, so use the latest prism release. rubocop stays at 1.79.1 so the workload is unchanged.