In gdb info file: 2.1.1 Choosing Files -------------------- Many options have both long and short forms; both are shown in the following list. GDB also recognizes the long forms if you truncate them, so long as enough of the option is present to be unambiguous. (If you prefer, you can flag option arguments with `--' rather than `-', though we illustrate the more usual convention.) In manual pages: -help -h List all options, with brief explanations. -symbols=file -s file Read symbol table from file file. ... SUGGESTION Please prefer listing the --long option names with two dashes (--) and not with single dash, although that may be still valid. The sinlge dash -option syntax is confusing, when compared to options that can be stacked e.g. in GNU ls(1) - laF...", not so in GNU gdb. The GNU tools traditionally use --option syntax in their manuals.
./gdb -h versus info '(gdb)Mode Options' Info nodes "Choosing modes" and "Startup', write about "-nx" with one dash, but "gdb -h" speaks about "--nx" with two dashes. Likewise for "-nh"/"--nh". gdb -h does not mention just "-n". In fact 'Choosing modes' mentions every option with one dash, while "gdb -h" states that only single-letter options are with one dash. All of the single-dash/double-dash long-name options I tried do work, but this does not justify inconsistent documentation.
Commit 2047d95b897c7153368033c318185429f7809e4f fixes this, so I'm closing this issue