Re: AC_CHECK_HEADER/AC_CHECK_DECL 2.69->2.69c probably changed quoting, breaks gimp as "...: ${+y}: bad substitution"

[Sergei Trofimovich]

On Sun, 25 Oct 2020 09:54:42 -0400
Zack Weinberg <zackw@panix.com> wrote:

> On Sun, Oct 25, 2020 at 9:13 AM Sergei Trofimovich <slyfox@gentoo.org> wrote:
> ...
> > gimp's use of macros looks underquoted  
> 
> Yes, this is an underquotation problem, and also a "macros that use
> AC_REQUIRE internally are not safe to use inside hand-coded shell
> conditionals" problem.  This particular example is so badly broken
> that I'm amazed it worked at all with 2.69.
> 
> The AC_ARG_WITH part is fine (although it could be improved by using
> AS_HELP_STRING) but the actual check should be done like this:
> 
> have_linux_input="no (linux input support disabled)"
> AS_IF([test "x$with_linux_input" != "xno"],
>   [AC_CHECK_HEADER([linux/input.h],
>     [AC_CHECK_DECL([KEY_OK],
>                    [have_linux_input=yes],
>                    [have_linux_input="no (needs Linux 2.6)"],
>                    [#include <linux/input.h>])])])
> 
> This kind of correction is, regrettably, beyond the power of autoupdate.
> 
> > but I would expect
> > behavior to be roughly the same between 2.69 and 2.69c.  
> 
> Unfortunately no.  There have been major changes since 2.69 in the way
> AC_CHECK_HEADER and AC_CHECK_DECL work, and this breakage appears to
> have been a consequence.  Looking at the diffs between the generated
> configure scripts, the underquoted version has shell function
> definitions intertwined with top-level control flow, because
> AC_CHECK_DECL was expanded first and then treated as *multiple
> arguments* to AC_CHECK_HEADER.  Plus, code that needs to be executed
> unconditionally was emitted inside the "if" block.

I was afraid of that. Looks like gimp's configure.ac will require a lot more
quotation cleanup. Meanwhile proposed your fix for 'linux-input' handling
fix as https://gitlab.gnome.org/GNOME/gimp/-/merge_requests/357

Thank you!

-- 

  Sergei