[Bug-tar] argp-help and program name

[Eric Blake]

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I noticed when compiling tar on cygwin that I got a warning:
if gcc -DHAVE_CONFIG_H -DLIBDIR=\"/usr/local/lib\" -I. -I. -I..     -g2
- -Wall -Werror -MT argp-help.o -MD -MP -MF ".deps/argp-help.Tpo" -c -o
argp-help.o argp-help.c; \
then mv -f ".deps/argp-help.Tpo" ".deps/argp-help.Po"; else rm -f
".deps/argp-help.Tpo"; exit 1; fi
argp-help.c:1693:4: #warning No reasonable value to return

Further looking at the argp-help module shows that tries using
strrchr(program_invocation_name, '/') which is not portable
to platforms with \ as a directory separator (it would be better
to use the dirname module).  Since the warning comes during the fallback
when program_invocation_name does not exist, and since tar uses the error
module which already expects program_name to exist, it would probably be
wise to change argp-help to use program_name in the same way that the
error module does.

- --
Life is short - so eat dessert first!

Eric Blake             address@hidden
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