The wrapper could not be parsed by a POSIX shell at all - dash stopped at line
39 on "function dummy ()". It coped by re-execing itself:
if [ -z "$BASH_VERSION" ]; then
exec bash "$0" "$@"
fi
which only works where bash exists. That is not everywhere we claim to build:
Alpine/musl images frequently have no bash, and FreeBSD keeps it in
/usr/local/bin. It also cannot help the case that matters most - incl/Makefile-
common sets SH=sh, so the makefiles run "${SH} .../bin/aubit fcompile ..." and
a shebang would be ignored there anyway. On any system where /bin/sh is dash,
those rules were relying on that exec finding a bash.
The script turned out to be very close to POSIX already - no [[ ]], no arrays,
no ${x//y}, no +=, no <<<, no brace expansion. What it used:
118 function NAME () -> NAME ()
44 let X=X+1 -> X=$((X+1))
6 echo -e -> printf '%b\n' (dash's echo expands escapes
itself and would have printed a literal "-e")
4 source F -> . F
4 declare X=Y -> local X=Y (matching the comment above them)
With those gone the re-exec is unnecessary and is removed, and the file gets a
real "#!/bin/sh" on line 1 - the one it had was on line 32, where it is just a
comment. The dummy() tripwire stays as a guard for a shell with no function
support at all, but its message no longer tells people to install bash, and it
no longer tries to run itself under a bash it may not have.
Verified rather than assumed: bin/aubit now parses under dash, bash and sh;
"aubit-config", "4glpc", "fcompile" and "amkmessage" all produce correct output
when driven by dash as well as bash; and tools/test builds end to end with
"make SH=/bin/dash SHELL=/bin/dash", which exercises the wrapper for form
compilation and message compilation. Before this change dash could not get past
parsing the file.
A full clean build is unaffected: 724 warnings, exit 0.
