Segfault after pressing Shift+F4

[linnando]

Actions to reproduce: press Shift+F4 (reproducibility may depend on the config; I got it on a freshly built instance, but I am not sure which config it pulled).

Expected result: open an editor window.

Actual result: segfault.

The segfault happens at ​https://github.com/MidnightCommander/mc/blob/5cae1ddd9a4dc80ace53d02da6843401eaeb4e7c/src/execute.c#L311 because argv is dereferenced unconditionally, even though ​https://github.com/MidnightCommander/mc/blob/5cae1ddd9a4dc80ace53d02da6843401eaeb4e7c/src/execute.c#L664 passes NULL as argv when parsing external_cmd_options fails.

A possible patch is here: ​https://github.com/linnando/mc/tree/fix-shiftf4-segfault

Output of mc -V:

GNU Midnight Commander 4.8.31
Built with GLib 2.82.1
Built with S-Lang 2.3.3 with terminfo database
Built with libssh2 1.11.0
With builtin Editor and Aspell support
With subshell support as default
With support for background operations
With mouse support on xterm and Linux console
With support for X11 events
With internationalization support
With multiple codepages support
With ext2fs attributes support
Virtual File Systems:

cpiofs, tarfs, sfs, extfs, ext2undelfs, ftpfs, sftpfs, shell

Data types:

char: 8; int: 32; long: 64; void *: 64; size_t: 64; off_t: 64;

[andrew_b]

#4580
Fixed in 4.8.33.

[andrew_b]

Sorry, this is another issue.
In any case, it's not reproducible for me in 4.8.33.

[linnando]

Yes, it is another issue. Unfortunately, for me it is the same in 4.8.33 and at the current master HEAD. I collected extra information about the reproduction, and the situation looks like that:

1. The critical part of the reproduction is entering the branch where g_shell_parse_argv cannot parse the provided argument extern_cmd_options (i.e., ​https://github.com/MidnightCommander/mc/blob/5cae1ddd9a4dc80ace53d02da6843401eaeb4e7c/src/execute.c#L664).
2. In my case, extern_cmd_options contain an empty string, which is enough for g_shell_parse_argv to return an error ("Text was empty (or contained only whitespace)" if I add debug info).
3. extern_cmd_options is an empty string because filename_vpath is an empty string, which in turn is caused by the configuration option 'Ask new file name' unchecked.
4. I tried checking 'Ask new file name' in the Options / Configuration... menu. In this case, Shift+F4 works correctly: asks for a file name, opens the editor, and allows me to save the file. However, with 'Ask new file name' unchecked, a segmentation fault happens after pressing Shift+F4 (the editor does not open). With the fix that I provided, Shift+F4 opens the editor, allows me to edit the file and asks for the file name before saving it.

[andrew_b]

Branch: 4650_shift_f4_segfault
changeset:ed0bf815035394e7cb8a750d85c57b36cc33bf75

[zaytsev]

Thank you!

[andrew_b]

Merged to master: [f2b482886711a1305abffdffa054216944453f3d].