Hello, On a recently guix-pulled system I observe an immediate crash when starting emacs: $ emacs -Q (process:20087): Gtk-WARNING **: Locale not supported by C library. Using the fallback 'C' locale. Fatal error 4: Illegal instruction Backtrace: /gnu/store/bk22dmj4x23h71pvpj1ndj5xdsm3mgdj-emacs-25.3/bin/emacs-25.3[0x504ac2] /gnu/store/bk22dmj4x23h71pvpj1ndj5xdsm3mgdj-emacs-25.3/bin/emacs-25.3[0x4ec4f9] /gnu/store/bk22dmj4x23h71pvpj1ndj5xdsm3mgdj-emacs-25.3/bin/emacs-25.3[0x503a5e] /gnu/store/bk22dmj4x23h71pvpj1ndj5xdsm3mgdj-emacs-25.3/bin/emacs-25.3[0x503c63] /gnu/store/bk22dmj4x23h71pvpj1ndj5xdsm3mgdj-emacs-25.3/bin/emacs-25.3[0x503d09] /gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/libpthread.so.0(+0x12000)[0x7f8ac12f7000] /gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/ld-linux-x86-64.so.2(+0x1ca1c)[0x7f8ac8606a1c] Illegal instruction With the help of OriansJ, I found that 1va3rsg2rjy75gmvfa5xkv2dw970ygaw-emacs-25.3.drv is the .drv that produces bk22dmj4x23h71pvpj1ndj5xdsm3mgdj-emacs-25.3; see attached. I have a working build of emacs in a previous profile generation -- 83rlg4n4slccqrgicpxgr38hgvxga5sh-emacs-25.3. It is produced by s4wyzhizmn858hvn3zmahmqi7ckphdgi-emacs-25.3.drv, also attached. I used gdb on the failing emacs: (gdb) bt #0 0x00007ffff7df4a1c in ?? () from /gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/ld-linux-x86-64.so.2 #1 0x00007fffefecbfbb in dlopen_doit () from /gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/lib/libdl.so.2 #2 0x00007ffff01f7901 in _dl_catch_error () from /gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/libc.so.6 #3 0x00007fffefecc599 in _dlerror_run () from /gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/lib/libdl.so.2 #4 0x00007fffefecc021 in dlopen@@GLIBC_2.2.5 () from /gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/lib/libdl.so.2 #5 0x00007fffec693e73 in g_module_open () from /gnu/store/sm37m59gq3smxxz8gs4jikn50qg0g7xh-glib-2.54.2/lib/libgmodule-2.0.so.0 #6 0x00007ffff6a18339 in _gtk_module_has_mixed_deps () from /gnu/store/gfz7znplsbgsw2npdbz5vgfl90q222hv-gtk+-3.22.26/lib/libgtk-3.so.0 #7 0x00007ffff69f0b32 in pre_parse_hook () from /gnu/store/gfz7znplsbgsw2npdbz5vgfl90q222hv-gtk+-3.22.26/lib/libgtk-3.so.0 #8 0x00007ffff4e6ef87 in g_option_context_parse () from /gnu/store/sm37m59gq3smxxz8gs4jikn50qg0g7xh-glib-2.54.2/lib/libglib-2.0.so.0 #9 0x00007ffff69f125a in gtk_parse_args () from /gnu/store/gfz7znplsbgsw2npdbz5vgfl90q222hv-gtk+-3.22.26/lib/libgtk-3.so.0 #10 0x00007ffff69f12fa in gtk_init_check () from /gnu/store/gfz7znplsbgsw2npdbz5vgfl90q222hv-gtk+-3.22.26/lib/libgtk-3.so.0 #11 0x00007ffff69f1359 in gtk_init () from /gnu/store/gfz7znplsbgsw2npdbz5vgfl90q222hv-gtk+-3.22.26/lib/libgtk-3.so.0 #12 0x00000000004cba84 in x_term_init () #13 0x00000000004cdc57 in Fx_open_connection () #14 0x000000000055d402 in Ffuncall () #15 0x00000000005907d3 in exec_byte_code () #16 0x000000000055d23b in Ffuncall () #17 0x000000000055e6dc in Fapply () #18 0x000000000055d329 in Ffuncall () #19 0x00000000005907d3 in exec_byte_code () #20 0x000000000055d23b in Ffuncall () #21 0x00000000005907d3 in exec_byte_code () #22 0x000000000055d23b in Ffuncall () #23 0x00000000005907d3 in exec_byte_code () #24 0x000000000055c358 in apply_lambda () #25 0x000000000055c67f in eval_sub () #26 0x000000000055fbe1 in Feval () #27 0x000000000055bc32 in internal_condition_case () #28 0x00000000004eef6c in top_level_1 () #29 0x000000000055bbd3 in internal_catch () #30 0x00000000004ec8f8 in command_loop () #31 0x00000000004f0e47 in recursive_edit_1 () #32 0x00000000004f1188 in Frecursive_edit () #33 0x000000000041abd1 in main () This indicates a problem in something GTK related. This is corroborated by terminal Emacs working: $ emacs -nw -Q --eval "(kill-emacs)" $ echo $? 0 And by other GTK apps crashing. Here's dino: (gdb) run Starting program: /gnu/store/d5104zb5s96mjcyycl2v68cnj6wmfl2j-dino-0.0-3.f25fadde2/bin/.dino-real [Thread debugging using libthread_db enabled] Using host libthread_db library "/gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/libthread_db.so.1". (process:10641): Gtk-WARNING **: Locale not supported by C library. Using the fallback 'C' locale. Program received signal SIGILL, Illegal instruction. 0x00007ffff7df4a1c in ?? () from /gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/ld-linux-x86-64.so.2 (gdb) bt #0 0x00007ffff7df4a1c in ?? () from /gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/ld-linux-x86-64.so.2 #1 0x00007ffff3c03fbb in dlopen_doit () from /gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/lib/libdl.so.2 #2 0x00007ffff426a901 in _dl_catch_error () from /gnu/store/n6acaivs0jwiwpidjr551dhdni5kgpcr-glibc-2.26.105-g0890d5379c/lib/libc.so.6 #3 0x00007ffff3c04599 in _dlerror_run () from /gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/lib/libdl.so.2 #4 0x00007ffff3c04021 in dlopen@@GLIBC_2.2.5 () from /gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/lib/libdl.so.2 #5 0x00007ffff775ee73 in g_module_open () from /gnu/store/sm37m59gq3smxxz8gs4jikn50qg0g7xh-glib-2.54.2/lib/libgmodule-2.0.so.0 #6 0x00007ffff6309339 in _gtk_module_has_mixed_deps () from /gnu/store/wsdqwpm22l8dgqqibzbgx5zn4bnkz0ci-gtk+-3.22.26/lib/libgtk-3.so.0 #7 0x00007ffff62e1b32 in pre_parse_hook () from /gnu/store/wsdqwpm22l8dgqqibzbgx5zn4bnkz0ci-gtk+-3.22.26/lib/libgtk-3.so.0 #8 0x00007ffff475ff87 in g_option_context_parse () from /gnu/store/sm37m59gq3smxxz8gs4jikn50qg0g7xh-glib-2.54.2/lib/libglib-2.0.so.0 #9 0x00007ffff62e225a in gtk_parse_args () from /gnu/store/wsdqwpm22l8dgqqibzbgx5zn4bnkz0ci-gtk+-3.22.26/lib/libgtk-3.so.0 #10 0x00007ffff62e22fa in gtk_init_check () from /gnu/store/wsdqwpm22l8dgqqibzbgx5zn4bnkz0ci-gtk+-3.22.26/lib/libgtk-3.so.0 #11 0x00007ffff62e2359 in gtk_init () from /gnu/store/wsdqwpm22l8dgqqibzbgx5zn4bnkz0ci-gtk+-3.22.26/lib/libgtk-3.so.0 #12 0x000000000041caa2 in dino_main () #13 0x000000000041c900 in main () Where can I go from here to debug this?