fix building old gcc with new gcc by using -std=gnu89

[urjaman]

I've been building some of these on arch. Not sure if this is everything thats needed for the gcc-539 ...
(i needed to build an older bison and set that in the path for something, but cant remember if it was for this.)

[mstorsjo]

I tried building gcc-539 with GCC 6 (on debian sid), and it seemed to work fine without this patch, so it seems it's probably not needed after all? (I guess GCC 6 is the version where the default language was changed.)

I'll try to do a clean docker test build env to verify that these things still build with recent tools...

[urjaman]

I think the default was changed atleast already in gcc 5, but the symptom was that I'd get
a c-lex.c:273: undefined reference to `is_reserved_word' and searching for that found people trying to compile an old 2.95 gcc with gcc 5.4.0 and the response was to use -std=gnu89, and it worked.

At first i thought it was debian doing weird stuff, but a "quck" test of getting a gcc 6 on debian shows that yeah they didnt mess with gcc like that... dunno what it exactly is then.

[mstorsjo]

Hmm, ok.

When trying to rebuild all of this on modern debian sid, I'm now running into issues with building the codesourcery GCC (3.4) with modern bison, failing on something like this:

c-parse.y: In function 'yyparse':
c-parse.y:594:16: error: 'YYLEX' undeclared (first use in this function)
       yychar = YYLEX;

Was this something that you happened to have seen? It seems like it could be caused by a too new bison version.

[urjaman]

Yes I have built that gcc 3.4 and I have as a workaround installed a bison 2.7.12-4996 in my personal ~/bin and set that first in the path, but obviously that isnt a very good solution.