Re: [PATCH] Fix build failure on macOS

[Simon Marchi <simark@simark.ca>]

On 2019-12-18 10:05 a.m., Tom Tromey wrote:
> PR build/25250 notes that the gdb 9 pre-release fails to build on
> macOS, due to a name clash between field_kind::STRING and the STRING
> token in ada-exp.y.  I am not sure (I couldn't reproduce this myself),
> but presumably this is due to differences caused by the version of
> bison in use there.
> 
> This patch works around the problem by renaming the field_kind
> enumerator.  I chose to rename this one because it is used in
> relatively few places -- it's just an implementation detail of the
> style code.
> 
> Let me know what you think.  I intend to check this in on the gdb 9
> branch as well.

The difference between macOS's bison (2.3) and later version (I'm not sure at
which release the behavior changed) is that the order of the prologue (where
we #include stuff) versus the bison declarations (#define STRING xyz) changed.
Bison 2.3 puts the declarations before the prologue, which can break included
files as we see here.  Later versions put the prologue before (actually the
exact location of the code can be controlled by using %code).

I don't really mind this particular fix, as it doesn't add complexity.  But if
in the future the macOS version gives us some more major headache, I would be
comfortable just saying that we don't support it, and adding a %require statement
in the grammar file.  Recent bison versions are easily available through Homebrew
and macports.

Simon