Style question on choosing shell variable names to use with the manywarnings module

[James Youngman]

Hi,

I'm  using gnulib's manywarnings module in findutils.   I have an
--enable-compiler-warning configure option which turns on the
warnings.   Since most people won't use this option, I call
gl_MANYWARN_ALL_GCC unconditionally to help discover systems on which
this doesn't work (none found yet!).   This means that $warnings is
set to the set of supported warnings, though later we remove some as
shown below.   However, I then use the value of $warnings inside the
"enabled" arm of AC_ARG_ENABLE.   So I have an implicit assumption
that no other code will use the shell variable ${warnings}.

Since the variable doesn't begin ac_ I know that Autoconf won't stamp
on it, and as I understand it since it doesn't begin gl_, gnulib won't
stamp on it.   Is doing things this way my best stylistic choice?

Here is the code I'm using (the code in findutils is very similar,
apart from some missing quoting that I will be fixing shortly).

# Enable various GCC warnings.
gl_MANYWARN_ALL_GCC([warnings])
# Set up the list of the pointless, undesired warnings.
nw=
nw="${nw} -Wsystem-headers"       # Don't let system headers trigger warnings
nw="${nw} -Wundef"                # All compiler preprocessors support #if UNDEF
nw="${nw} -Wtraditional"          # All compilers nowadays support ANSI C
nw="${nw} -Wconversion"           # These warnings usually don't point
to mistakes.
nw="${nw} -Wsign-conversion"      # Likewise.
nw="${nw} -Wc++-compat"           # malloc returns void* and a cast
would be ugly.
# Warnings we might enable in the future, but not yet (because they generate a
# lot of noise).
marginal=""
marginal="${marginal} -Wtraditional-conversion"
marginal="${marginal} -Wpadded"
marginal="${marginal} -Wformat-nonliteral"
marginal="${marginal} -Wunreachable-code"
marginal="${marginal} -Wunused-parameter"
excluded_warnings="${nw} ${marginal}"

# Enable all GCC warnings not in this list.
gl_MANYWARN_COMPLEMENT([warnings], [${warnings}], [${excluded_warnings}])

AC_ARG_ENABLE(compiler-warnings,
  AS_HELP_STRING(--enable-compiler-warnings,Enable many compiler warnings),
  [
  for w in ${warnings}
  do
    gl_WARN_ADD([${w}])
  done
  ]
)

Thanks,
James.


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