error: failed to run custom build command for `pcre2-sys v0.2.6` on the centos7 platform

[Peefy]

Description

I have failed to run custom build command for pcre2-sys v0.2.6 on the centos7 platform.

The error message is

warning: upstream/src/pcre2_script_run.c: In function '_pcre2_script_run_8':
warning: upstream/src/pcre2_script_run.c:109:1: error: 'for' loop initial declarations are only allowed in C99 mode
warning:  for (int i = 0; i < FULL_MAPSIZE; i++) require_map[i] = 0;
warning:  ^
warning: upstream/src/pcre2_script_run.c:109:1: note: use option -std=c99 or -std=gnu99 to compile your code
warning: upstream/src/pcre2_script_run.c:248:7: error: 'for' loop initial declarations are only allowed in C99 mode
warning:        for (int i = 0; i < FULL_MAPSIZE; i++)
warning:        ^
warning: upstream/src/pcre2_script_run.c:285:9: error: 'for' loop initial declarations are only allowed in C99 mode
warning:          for (int i = 0; i < FULL_MAPSIZE; i++) require_map[i] &= map[i];
warning:          ^

error: failed to run custom build command for `pcre2-sys v0.2.6`

[Peefy]

If possible, I can fix it

[Peefy]

To walk-around it, I enabled export CC=c99

[BurntSushi]

It's unclear to me why this is failing on CentOS but not anywhere else. I don't have a CentOS 7 system I can easily test on, so I think this will probably a require someone other than me to submit a patch.

[Peefy]

I guess it's caused by a lower version of gcc. Could I open a PR to set 'cc' crate with c99 mode by default?

[BurntSushi]

The lower version might indeed be the culprit, although I still find that curious. Does that imply more recent versions of gcc default to at least c99? And the CentOS version of gcc does not? That feels like a question with a definite answer to me.

But either way, yes, I think setting C99 mode explicitly in the build script is fine as long as CI passes.

[Peefy]

The lower version might indeed be the culprit, although I still find that curious. Does that imply more recent versions of gcc default to at least c99? And the CentOS version of gcc does not? That feels like a question with a definite answer to me.

But either way, yes, I think setting C99 mode explicitly in the build script is fine as long as CI passes.

Ok I will Open a PR to set C99 mode later

[cuviper]

The lower version might indeed be the culprit, although I still find that curious. Does that imply more recent versions of gcc default to at least c99? And the CentOS version of gcc does not? That feels like a question with a definite answer to me.

Yes, CentOS 7's gcc is 4.8.5, where:

The default, if no C language dialect options are given, is -std=gnu90; this will change to -std=gnu99 or -std=gnu11 in some future release when the C99 or C11 support is complete.

And indeed 5.1.0 changed to -std=gnu11. Then 11.1.0 stepped up to -std=gnu17, where it remains today.

(CentOS 7 has passed EOL, but RHEL 7 ELS remains until 2028.)