Re: [PATCH] Modernize more C programs in config.guess.

[Jacob Bachmeyer]

Zack Weinberg wrote:
> From: Zack Weinberg <zack@owlfolio.org>
>
> Specifically, on top of Petr Vorel’s patch, eliminate all use of
> old-style function definitions and implicit function declarations.
>
> Many of the C programs embedded in config.guess are only used on very
> old systems that may never have had an ISO C compiler (other than gcc,
> which we cannot assume has been installed) so we have to do this
> carefully.  I assume that stdio.h exists unconditionally, and that
> either it declares puts and printf, or the compiler is so old that
> implicit function declarations are the order of the day.  I also
> assume it is safe to declare main as ‘int main (void)’; that may need
> to get reverted.  All uses of ‘exit’ are replaced with returning from
> main, so that we do not need to worry about whether stdlib.h exists.
>
> The only C program that took command line arguments, and therefore
> needed to declare main with arguments, is replaced with a
> preprocessor-only check and string manipulation from shell.
>
> Wherever possible, uses of printf are demoted to puts.
> ---
>  config.guess | 111 ++++++++++++++++++++++++---------------------------
>  1 file changed, 52 insertions(+), 59 deletions(-)
>
> diff --git a/config.guess b/config.guess
> index ff5146b..1059f76 100755
> --- a/config.guess
> +++ b/config.guess
> @@ -4,7 +4,7 @@
>  
>  # shellcheck disable=SC2006,SC2268 # see below for rationale
>  
> -timestamp='2024-01-03'
> +timestamp='2024-04-04'
>  
>  # This file is free software; you can redistribute it and/or modify it
>  # under the terms of the GNU General Public License as published by
> @@ -534,29 +534,22 @@ case 
> $UNAME_MACHINE:$UNAME_SYSTEM:$UNAME_RELEASE:$UNAME_VERSION in
>      mips:*:*:UMIPS | mips:*:*:RISCos)
>         set_cc_for_build
>         sed 's/^        //' << EOF > "$dummy.c"
> [...]
>  EOF
> -       $CC_FOR_BUILD -o "$dummy" "$dummy.c" &&
> -         dummyarg=`echo "$UNAME_RELEASE" | sed -n 's/\([0-9]*\).*/\1/p'` &&
> -         SYSTEM_NAME=`"$dummy" "$dummyarg"` &&
> +       SYSTEM_TYPE="`$CC_FOR_BUILD -E - < "$dummy.c" |
> +           sed -n 's/^ *SYSTYPE *= *//p'`" &&
> +       SYSTEM_REL="`echo "$UNAME_RELEASE" | sed -n 's/\([0-9]*\).*/\1/p'`" &&
> +       SYSTEM_NAME="mips-mips-riscos${SYSTEM_REL}${SYSTEM_TYPE}" &&
>   

You have tripped up on a known portability issue here:  due to bugs in 
various shells, there is no portable way to use double quotes inside 
double-quoted backticks.  Since word-splitting is not done on variable 
assignments, the simplest solution is to remove the outermost double 
quotes, like so:

SYSTEM_TYPE=`$CC_FOR_BUILD -E - < "$dummy.c" | sed -n 's/^ *SYSTYPE *= *//p'` &&
SYSTEM_REL=`echo "$UNAME_RELEASE" | sed -n 's/\([0-9]*\).*/\1/p'` &&
SYSTEM_NAME=mips-mips-riscos${SYSTEM_REL}${SYSTEM_TYPE} && 

There are reasons that variable assignments in config.guess usually omit 
unnecessary quotes, mostly due to bugs in ancient shells under which 
config.guess still needs to be able to run.
> [...]
> @@ -793,20 +782,25 @@ EOF
> [...]
> -       $CC_FOR_BUILD -o "$dummy" "$dummy.c" && SYSTEM_NAME=`"$dummy"` &&
> -               { echo "$SYSTEM_NAME"; exit; }
> +       if $CC_FOR_BUILD -o "$dummy" "$dummy.c" && SYSTEM_CPU=`"$dummy"`; then
> +           if [ "$SYSTEM_CPU" != "unknown" ]; then
> +               SYSTEM_NAME="${SYSTEM_CPU}-hitachi-hiuxwe2"
>   
Once again, this should be:

SYSTEM_NAME=${SYSTEM_CPU}-hitachi-hiuxwe2

We could argue style all day long, but this script has to run under 
ancient shells (because it is supposed to identify archaic systems) and 
all other assignments avoid unneeded quotes.


-- Jacob