-std=gnu99 causes annoying warnings

[vicuna]

Original bug ID: 7377
Reporter: @ygrek
Status: resolved (set by @xavierleroy on 2016-12-05T08:41:31Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 4.03.0
Target version: 4.05.0 +dev/beta1/beta2/beta3/rc1
Fixed in version: 4.05.0 +dev/beta1/beta2/beta3/rc1
Category: ~DO NOT USE (was: OCaml general)
Monitored by: @gasche

Bug description

Problem 1

When compiling c++ code via ocamlc (passing -ccopt -xc++ to tell gcc treat .c file as c++ code) gcc will complain that gnu99 applies to C code only

Problem 2

With gcc 6 (for example) default C standard is gnu11 and -std=gnu99 becomes too pessimistic and may cause code to fail (theory - didn't observe this).

One way to fix this would be to remove this option from native_c_compiler and require users to supply a C99 supporting compiler at configure time explicitly if needed (with -cc "gcc -std=gnu99") - this will solve problem 1 for us because we use newer gcc anyway.

[vicuna]

Comment author: @damiendoligez

I think the solution is to remove the -std=gnu99 option when using gcc 5 and later (which default to gnu11).

I've created #876 ( #876 ) against trunk because I think this is a bit too risky to fix just before the release.

[vicuna]

Comment author: @xavierleroy

Fixed in commit 4c03ef7 as part of #876.