I verified the fix by building 21.4.22 from the original source tarball, reproducing the crash, applying the patch, and trying to reproduce the crash. Here's the stack information from gdb: (gdb) run -vanilla The program being debugged has been started already. Start it from the beginning? (y or n) y Starting program: /usr/bin/xemacs -vanilla [Thread debugging using libthread_db enabled] Warning: Cannot convert string "-*-helvetica-bold-r-*-*-*-120-*-*-*-*-iso8859-*" to type FontStruct *** glibc detected *** /usr/bin/xemacs: munmap_chunk(): invalid pointer: 0x000000000124fac0 *** ======= Backtrace: ========= /lib/x86_64-linux-gnu/libc.so.6(+0x78a96)[0x7ffff5121a96] /lib/x86_64-linux-gnu/libz.so.1(inflateEnd+0x34)[0x7ffff4a8b424] /lib/x86_64-linux-gnu/libpng12.so.0(png_read_destroy+0x21f)[0x7ffff76f4bbf] /lib/x86_64-linux-gnu/libpng12.so.0(png_destroy_read_struct+0x7a)[0x7ffff76f4e5a] /usr/bin/xemacs[0x4d4c24] /usr/bin/xemacs(unbind_to_hairy+0x63)[0x470883] /usr/bin/xemacs(unbind_to+0x86)[0x470966] /usr/bin/xemacs[0x4d5428] /usr/bin/xemacs[0x4d0c84] /usr/bin/xemacs[0x4d2cf9] /usr/bin/xemacs[0x472436] /usr/bin/xemacs(internal_catch+0xb1)[0x471211] /usr/bin/xemacs(call_with_suspended_errors+0x224)[0x477194] /usr/bin/xemacs[0x529486] /usr/bin/xemacs(specifier_instance+0x2a1)[0x529911] /usr/bin/xemacs(glyph_image_instance+0x27)[0x4cda57] /usr/bin/xemacs(glyph_width+0x16)[0x4cffb6] /usr/bin/xemacs(Fglyph_width+0x21)[0x4d0301] /usr/bin/xemacs(Ffuncall+0x44e)[0x473cae] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x4bdda5] /usr/bin/xemacs(Fmapcar+0xf9)[0x4c0019] /usr/bin/xemacs(Ffuncall+0x44e)[0x473cae] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(Fbyte_code+0xaa)[0x452afa] /usr/bin/xemacs(Feval+0x971)[0x475a31] /usr/bin/xemacs(condition_case_1+0x113)[0x4774a3] /usr/bin/xemacs(execute_rare_opcode+0x1e6)[0x451776] /usr/bin/xemacs[0x452925] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs[0x452805] /usr/bin/xemacs(funcall_compiled_function+0x17c)[0x452ccc] /usr/bin/xemacs(Ffuncall+0x345)[0x473ba5] /usr/bin/xemacs(apply1+0x7f)[0x4750af] /usr/bin/xemacs(Fcall_interactively+0x1467)[0x4546e7] /usr/bin/xemacs(Fcommand_execute+0x17f)[0x47676f] /usr/bin/xemacs[0x4a237d] /usr/bin/xemacs(Fdispatch_event+0x172)[0x4a4082] /usr/bin/xemacs(Fcommand_loop_1+0x10b)[0x45864b] /usr/bin/xemacs(condition_case_1+0x113)[0x4774a3] /usr/bin/xemacs[0x458880] /usr/bin/xemacs(internal_catch+0xb1)[0x471211] ======= Memory map: ======== 00400000-005c3000 r-xp 00000000 08:02 6041540 /usr/bin/xemacs-21.4.22-nomule 007c2000-007c3000 r--p 001c2000 08:02 6041540 /usr/bin/xemacs-21.4.22-nomule 007c3000-007dc000 rw-p 001c3000 08:02 6041540 /usr/bin/xemacs-21.4.22-nomule 007dc000-01285000 rw-p 00000000 00:00 0 [heap] 7ffff03d5000-7ffff03ea000 r-xp 00000000 08:02 21499555 /lib/x86_64-linux-gnu/libgcc_s.so.1 7ffff03ea000-7ffff05e9000 ---p 00015000 08:02 21499555 /lib/x86_64-linux-gnu/libgcc_s.so.1 7ffff05e9000-7ffff05ea000 r--p 00014000 08:02 21499555 /lib/x86_64-linux-gnu/libgcc_s.so.1 7ffff05ea000-7ffff05eb000 rw-p 00015000 08:02 21499555 /lib/x86_64-linux-gnu/libgcc_s.so.1 7ffff05eb000-7ffff05f0000 r-xp 00000000 08:02 6036419 /usr/lib/x86_64-linux-gnu/libXfixes.so.3.1.0 7ffff05f0000-7ffff07ef000 ---p 00005000 08:02 6036419 /usr/lib/x86_64-linux-gnu/libXfixes.so.3.1.0 7ffff07ef000-7ffff07f0000 r--p 00004000 08:02 6036419 /usr/lib/x86_64-linux-gnu/libXfixes.so.3.1.0 7ffff07f0000-7ffff07f1000 rw-p 00005000 08:02 6036419 /usr/lib/x86_64-linux-gnu/libXfixes.so.3.1.0 7ffff07f1000-7ffff07fa000 r-xp 00000000 08:02 6036429 /usr/lib/x86_64-linux-gnu/libXrender.so.1.3.0 7ffff07fa000-7ffff09fa000 ---p 00009000 08:02 6036429 /usr/lib/x86_64-linux-gnu/libXrender.so.1.3.0 7ffff09fa000-7ffff09fb000 r--p 00009000 08:02 6036429 /usr/lib/x86_64-linux-gnu/libXrender.so.1.3.0 7ffff09fb000-7ffff09fc000 rw-p 0000a000 08:02 6036429 /usr/lib/x86_64-linux-gnu/libXrender.so.1.3.0 7ffff09fc000-7ffff0a05000 r-xp 00000000 08:02 6036411 /usr/lib/x86_64-linux-gnu/libXcursor.so.1.0.2 7ffff0a05000-7ffff0c04000 ---p 00009000 08:02 6036411 /usr/lib/x86_64-linux-gnu/libXcursor.so.1.0.2 7ffff0c04000-7ffff0c05000 r--p 00008000 08:02 6036411 /usr/lib/x86_64-linux-gnu/libXcursor.so.1.0.2 7ffff0c05000-7ffff0c06000 rw-p 00009000 08:02 6036411 /usr/lib/x86_64-linux-gnu/libXcursor.so.1.0.2 7ffff0c06000-7ffff179f000 rw-p 00000000 00:00 0 7ffff179f000-7ffff17a9000 r-xp 00000000 08:02 21499579 /lib/x86_64-linux-gnu/libnss_nis-2.13.so 7ffff17a9000-7ffff19a9000 ---p 0000a000 08:02 21499579 /lib/x86_64-linux-gnu/libnss_nis-2.13.so 7ffff19a9000-7ffff19aa000 r--p 0000a000 08:02 21499579 /lib/x86_64-linux-gnu/libnss_nis-2.13.so 7ffff19aa000-7ffff19ab000 rw-p 0000b000 08:02 21499579 /lib/x86_64-linux-gnu/libnss_nis-2.13.so 7ffff19ab000-7ffff19c2000 r-xp 00000000 08:02 21499569 /lib/x86_64-linux-gnu/libnsl-2.13.so 7ffff19c2000-7ffff1bc1000 ---p 00017000 08:02 21499569 /lib/x86_64-linux-gnu/libnsl-2.13.so 7ffff1bc1000-7ffff1bc2000 r--p 00016000 08:02 21499569 /lib/x86_64-linux-gnu/libnsl-2.13.so 7ffff1bc2000-7ffff1bc3000 rw-p 00017000 08:02 21499569 /lib/x86_64-linux-gnu/libnsl-2.13.so 7ffff1bc3000-7ffff1bc5000 rw-p 00000000 00:00 0 7ffff1bc5000-7ffff1bcd000 r-xp 00000000 08:02 21499571 /lib/x86_64-linux-gnu/libnss_compat-2.13.so 7ffff1bcd000-7ffff1dcc000 ---p 00008000 08:02 21499571 /lib/x86_64-linux-gnu/libnss_compat-2.13.so 7ffff1dcc000-7ffff1dcd000 r--p 00007000 08:02 21499571 /lib/x86_64-linux-gnu/libnss_compat-2.13.so 7ffff1dcd000-7ffff1dce000 rw-p 00008000 08:02 21499571 /lib/x86_64-linux-gnu/libnss_compat-2.13.so 7ffff1dce000-7ffff1dda000 r-xp 00000000 08:02 21499575 /lib/x86_64-linux-gnu/libnss_files-2.13.so 7ffff1dda000-7ffff1fd9000 ---p 0000c000 08:02 21499575 /lib/x86_64-linux-gnu/libnss_files-2.13.so 7ffff1fd9000-7ffff1fda000 r--p 0000b000 08:02 21499575 /lib/x86_64-linux-gnu/libnss_files-2.13.so 7ffff1fda000-7ffff1fdb000 rw-p 0000c000 08:02 21499575 /lib/x86_64-linux-gnu/libnss_files-2.13.so 7ffff1fdb000-7ffff2362000 rw-p 00000000 08:02 11796993 /usr/lib/xemacs-21.4.22/x86_64-linux-gnu/nomule/DUMP 7ffff2362000-7ffff2364000 r-xp 00000000 08:02 21499563 /lib/x86_64-linux-gnu/libkeyutils.so.1.3 7ffff2364000-7ffff2563000 ---p 00002000 08:02 21499563 /lib/x86_64-linux-gnu/libkeyutils.so.1.3 7ffff2563000-7ffff2564000 r--p 00001000 08:02 21499563 /lib/x86_64-linux-gnu/libkeyutils.so.1.3 7ffff2564000-7ffff2565000 rw-p 00002000 08:02 21499563 /lib/x86_64-linux-gnu/libkeyutils.so.1.3 7ffff2565000-7ffff2568000 r-xp 00000000 08:02 21499561 /lib/x86_64-linux-gnu/libgpg-error.so.0.8.0 7ffff2568000-7ffff2767000 ---p 00003000 08:02 21499561 /lib/x86_64-linux-gnu/libgpg-error.so.0.8.0 7ffff2767000-7ffff2768000 r--p 00002000 08:02 21499561 /lib/x86_64-linux-gnu/libgpg-error.so.0.8.0 7ffff2768000-7ffff2769000 rw-p 00003000 08:02 21499561 /lib/x86_64-linux-gnu/libgpg-error.so.0.8.0 7ffff2769000-7ffff2779000 r-xp 00000000 08:02 6036674 /usr/lib/x86_64-linux-gnu/libtasn1.so.3.1.11 7ffff2779000-7ffff2978000 ---p 00010000 08:02 6036674 /usr/lib/x86_64-linux-gnu/libtasn1.so.3.1.11 7ffff2978000-7ffff2979000 r--p 0000f000 08:02 6036674 /usr/lib/x86_64-linux-gnu/libtasn1.so.3.1.11 7ffff2979000-7ffff297a000 rw-p 00010000 08:02 6036674 /usr/lib/x86_64-linux-gnu/libtasn1.so.3.1.11 7ffff297a000-7ffff2981000 r-xp 00000000 08:02 6035451 /usr/lib/x86_64-linux-gnu/libkrb5support.so.0.1 7ffff2981000-7ffff2b80000 ---p 00007000 08:02 6035451 /usr/lib/x86_64-linux-gnu/libkrb5support.so.0.1 7ffff2b80000-7ffff2b81000 r--p 00006000 08:02 6035451 /usr/lib/x86_64-linux-gnu/libkrb5support.so.0.1 7ffff2b81000-7ffff2b82000 rw-p 00007000 08:02 6035451 /usr/lib/x86_64-linux-gnu/libkrb5support.so.0.1 7ffff2b82000-7ffff2b85000 r-xp 00000000 08:02 21499539 /lib/x86_64-linux-gnu/libcom_err.so.2.1 7ffff2b85000-7ffff2d84000 ---p 00003000 08:02 21499539 /lib/x86_64-linux-gnu/libcom_err.so.2.1 7ffff2d84000-7ffff2d85000 r--p 00002000 08:02 21499539 /lib/x86_64-linux-gnu/libcom_err.so.2.1 7ffff2d85000-7ffff2d86000 rw-p 00003000 08:02 21499539 /lib/x86_64-linux-gnu/libcom_err.so.2.1 7ffff2d86000-7ffff2dac000 r-xp 00000000 08:02 6035439 /usr/lib/x86_64-linux-gnu/libk5crypto.so.3.1 7ffff2dac000-7ffff2fab000 ---p 00026000 08:02 6035439 /usr/lib/x86_64-linux-gnu/libk5crypto.so.3.1 7ffff2fab000-7ffff2fad000 r--p 00025000 08:02 6035439 /usr/lib/x86_64-linux-gnu/libk5crypto.so.3.1 7ffff2fad000-7ffff2fae000 rw-p 00027000 08:02 6035439 /usr/lib/x86_64-linux-gnu/libk5crypto.so.3.1 7ffff2fae000-7ffff306d000 r-xp 00000000 08:02 6035445 /usr/lib/x86_64-linux-gnu/libkrb5.so.3.3 7ffff306d000-7ffff326d000 ---p 000bf000 08:02 6035445 /usr/lib/x86_64-linux-gnu/libkrb5.so.3.3 7ffff326d000-7ffff3276000 r--p 000bf000 08:02 6035445 /usr/lib/x86_64-linux-gnu/libkrb5.so.3.3 7ffff3276000-7ffff3277000 rw-p 000c8000 08:02 6035445 /usr/lib/x86_64-linux-gnu/libkrb5.so.3.3 7ffff3277000-7ffff327c000 r-xp 00000000 08:02 6036415 /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0 7ffff327c000-7ffff347b000 ---p 00005000 08:02 6036415 /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0 7ffff347b000-7ffff347c000 r--p 00004000 08:02 6036415 /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0 7ffff347c000-7ffff347d000 rw-p 00005000 08:02 6036415 /usr/lib/x86_64-linux-gnu/libXdmcp.so.6.0.0 7ffff347d000-7ffff347f000 r-xp 00000000 08:02 6036407 /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0 7ffff347f000-7ffff367e000 ---p 00002000 08:02 6036407 /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0 7ffff367e000-7ffff367f000 r--p 00001000 08:02 6036407 /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0 7ffff367f000-7ffff3680000 rw-p 00002000 08:02 6036407 /usr/lib/x86_64-linux-gnu/libXau.so.6.0.0 7ffff3680000-7ffff36fa000 r-xp 00000000 08:02 21499557 /lib/x86_64-linux-gnu/libgcrypt.so.11.7.0 7ffff36fa000-7ffff38fa000 ---p 0007a000 08:02 21499557 /lib/x86_64-linux-gnu/libgcrypt.so.11.7.0 7ffff38fa000-7ffff38fb000 r--p 0007a000 08:02 21499557 /lib/x86_64-linux-gnu/libgcrypt.so.11.7.0 7ffff38fb000-7ffff38fe000 rw-p 0007b000 08:02 21499557 /lib/x86_64-linux-gnu/libgcrypt.so.11.7.0 7ffff38fe000-7ffff399f000 r-xp 00000000 08:02 6036535 /usr/lib/x86_64-linux-gnu/libgnutls.so.26.16.14 7ffff399f000-7ffff3b9e000 ---p 000a1000 08:02 6036535 /usr/lib/x86_64-linux-gnu/libgnutls.so.26.16.14 7ffff3b9e000-7ffff3ba5000 r--p 000a0000 08:02 6036535 /usr/lib/x86_64-linux-gnu/libgnutls.so.26.16.14 7ffff3ba5000-7ffff3ba6000 rw-p 000a7000 08:02 6036535 /usr/lib/x86_64-linux-gnu/libgnutls.so.26.16.14 7ffff3ba6000-7ffff3be1000 r-xp 00000000 08:02 6035443 /usr/lib/x86_64-linux-gnu/libgssapi_krb5.so.2.2 7ffff3be1000-7ffff3de1000 ---p 0003b000 08:02 6035443 /usr/lib/x86_64-linux-gnu/libgssapi_krb5.so.2.2 7ffff3de1000-7ffff3de2000 r--p 0003b000 08:02 6035443 /usr/lib/x86_64-linux-gnu/libgssapi_krb5.so.2.2 7ffff3de2000-7ffff3de4000 rw-p 0003c000 08:02 6035443 /usr/lib/x86_64-linux-gnu/libgssapi_krb5.so.2.2 7ffff3de4000-7ffff3dfe000 r-xp 00000000 08:02 6036653 /usr/lib/x86_64-linux-gnu/libsasl2.so.2.0.24 7ffff3dfe000-7ffff3ffd000 ---p 0001a000 08:02 6036653 /usr/lib/x86_64-linux-gnu/libsasl2.so.2.0.24 7ffff3ffd000-7ffff3ffe000 r--p 00019000 08:02 6036653 /usr/lib/x86_64-linux-gnu/libsasl2.so.2.0.24 7ffff3ffe000-7ffff3fff000 rw-p 0001a000 08:02 6036653 /usr/lib/x86_64-linux-gnu/libsasl2.so.2.0.24 7ffff3fff000-7ffff4016000 r-xp 00000000 08:02 21499596 /lib/x86_64-linux-gnu/libresolv-2.13.so 7ffff4016000-7ffff4216000 ---p 00017000 08:02 21499596 /lib/x86_64-linux-gnu/libresolv-2.13.so 7ffff4216000-7ffff4217000 r--p 00017000 08:02 21499596 /lib/x86_64-linux-gnu/libresolv-2.13.so 7ffff4217000-7ffff4218000 rw-p 00018000 08:02 21499596 /lib/x86_64-linux-gnu/libresolv-2.13.so 7ffff4218000-7ffff421a000 rw-p 00000000 00:00 0 7ffff421a000-7ffff423c000 r-xp 00000000 08:02 21495904 /lib/libtinfo.so.5.9 7ffff423c000-7ffff443c000 ---p 00022000 08:02 21495904 /lib/libtinfo.so.5.9 7ffff443c000-7ffff4440000 r--p 00022000 08:02 21495904 /lib/libtinfo.so.5.9 7ffff4440000-7ffff4441000 rw-p 00026000 08:02 21495904 /lib/libtinfo.so.5.9 7ffff4441000-7ffff4459000 r-xp 00000000 08:02 21499594 /lib/x86_64-linux-gnu/libpthread-2.13.so 7ffff4459000-7ffff4658000 ---p 00018000 08:02 21499594 /lib/x86_64-linux-gnu/libpthread-2.13.so 7ffff4658000-7ffff4659000 r--p 00017000 08:02 21499594 /lib/x86_64-linux-gnu/libpthread-2.13.so 7ffff4659000-7ffff465a000 rw-p 00018000 08:02 21499594 /lib/x86_64-linux-gnu/libpthread-2.13.so 7ffff465a000-7ffff465e000 rw-p 00000000 00:00 0 7ffff465e000-7ffff4662000 r-xp 00000000 08:02 21499613 /lib/x86_64-linux-gnu/libuuid.so.1.3.0 7ffff4662000-7ffff4861000 ---p 00004000 08:02 21499613 /lib/x86_64-linux-gnu/libuuid.so.1.3.0 7ffff4861000-7ffff4862000 r--p 00003000 08:02 21499613 /lib/x86_64-linux-gnu/libuuid.so.1.3.0 7ffff4862000-7ffff4863000 rw-p 00004000 08:02 21499613 /lib/x86_64-linux-gnu/libuuid.so.1.3.0 7ffff4863000-7ffff487e000 r-xp 00000000 08:02 6036703 /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0 7ffff487e000-7ffff4a7d000 ---p 0001b000 08:02 6036703 /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0 7ffff4a7d000-7ffff4a7e000 r--p 0001a000 08:02 6036703 /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0 7ffff4a7e000-7ffff4a7f000 rw-p 0001b000 08:02 6036703 /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0 7ffff4a7f000-7ffff4a96000 r-xp 00000000 08:02 21499617 /lib/x86_64-linux-gnu/libz.so.1.2.3.4 7ffff4a96000-7ffff4c95000 ---p 00017000 08:02 21499617 /lib/x86_64-linux-gnu/libz.so.1.2.3.4 7ffff4c95000-7ffff4c96000 r--p 00016000 08:02 21499617 /lib/x86_64-linux-gnu/libz.so.1.2.3.4 7ffff4c96000-7ffff4c97000 rw-p 00017000 08:02 21499617 /lib/x86_64-linux-gnu/libz.so.1.2.3.4 Program received signal SIGABRT, Aborted. 0x00007ffff50df3a5 in raise () from /lib/x86_64-linux-gnu/libc.so.6 (gdb)