native-compile the problematic file after setting the variable
'comp-libgccjit-reproducer' to a non-nil value. That should produce a
file named ELNFILENAME_libgccjit_repro.c, where ELNFILENAME is the
-name of the problematic .eln file in the same directory where the .eln
-file is produced, or a file repro.c under your ~/.emacs.d/eln-cache
-(which one depends on how the native-compilation is invoked). Then
-attach that reproducer C file to your bug report.
+name of the problematic .eln file, either in the same directory where
+the .eln file is produced, or under your ~/.emacs.d/eln-cache (which
+one depends on how the native-compilation is invoked). It is also
+possible that the reproducer file's name will be something like
+subr--trampoline-XXXXXXX_FUNCTION_libgccjit_repro.c, where XXXXXXX is
+a long string of hex digits and FUNCTION is some function from the
+compiled .el file. Attach that reproducer C file to your bug report.
** Following longjmp call.