In pikefarm, the devel2 host has gcc-6 and gcc-7 (Debian 7.2.0-19); by default it picks gcc-7 and then fails. Manually compiling with gcc-6 works, I think I already tried gcc-7 using -O1, and that also works.
Still trying to investigate why exactly. The only visible odd warning during compilation is this one:
Compiling backend.c In file included from /var/src/roxen/81pike/src/array.h:10:0, from /var/src/roxen/81pike/src/callback.h:10, from /var/src/roxen/81pike/src/backend.h:11, from /var/src/roxen/81pike/src/backend.cmod:13: /var/src/roxen/81pike/src/backend.cmod: In function ‘f_Backend_get_stats’: /var/src/roxen/81pike/src/svalue.h:753:13: warning: iteration 9223372036854775807 invokes undefined behavior [-Waggressive-loop-optimizations] while(num_--) \ ~~~~^ /var/src/roxen/81pike/src/interpret.h:265:6: note: in expansion of macro ‘free_mixed_svalues’ free_mixed_svalues(_sp_, x_); \ ^~~~~~~~~~~~~~~~~~ /var/src/roxen/81pike/src/interpret.h:279:7: note: in expansion of macro ‘pop_n_elems’ pop_n_elems (x2_ - 1); \ ^~~~~~~~~~~ /var/src/roxen/81pike/src/interpret.h:283:39: note: in expansion of macro ‘stack_unlink’ #define stack_pop_n_elems_keep_top(X) stack_unlink(X) ^~~~~~~~~~~~ /var/src/roxen/81pike/src/backend.cmod:947:1: note: in expansion of macro ‘stack_pop_n_elems_keep_top’ stack_pop_n_elems_keep_top(args); ^ ~~~~~~~~~~~~~~~~~~~~~~ /var/src/roxen/81pike/src/svalue.h:753:8: note: within this loop while(num_--) \ ^ /var/src/roxen/81pike/src/interpret.h:265:6: note: in expansion of macro ‘free_mixed_svalues’ free_mixed_svalues(_sp_, x_); \ ^~~~~~~~~~~~~~~~~~ /var/src/roxen/81pike/src/interpret.h:279:7: note: in expansion of macro ‘pop_n_elems’ pop_n_elems (x2_ - 1); \ ^~~~~~~~~~~ /var/src/roxen/81pike/src/interpret.h:283:39: note: in expansion of macro ‘stack_unlink’ #define stack_pop_n_elems_keep_top(X) stack_unlink(X) ^~~~~~~~~~~~ /var/src/roxen/81pike/src/backend.cmod:947:1: note: in expansion of macro ‘stack_pop_n_elems_keep_top’ stack_pop_n_elems_keep_top(args); ^ ~~~~~~~~~~~~~~~~~~~~~~