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Date: Thu, 01 Aug 2024 23:26:10 +0100
To: internals@lists.php.net
Subject: Re: [PHP-DEV] Require C11 in PHP 8.4
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From: derick@php.net (Derick Rethans)

On 1 August 2024 22:57:36 BST, Ilija Tovilo <tovilo=2Eilija@gmail=2Ecom> wr=
ote:
>Hi everyone
>
>We've gotten a bug report about compile errors in the PHP 8=2E4 alpha on
>old C99 compilers (and on some modern compilers when passing the
>-std=3Dc99 flag)=2E Specifically, C99 does not support typedef
>redeclarations, which is a C11 feature=2E
>
>```c
>// some_header=2Eh
>typedef struct _zval_struct zval;
>void some_func(zval *zv);
>
>// zend_types=2Eh
>struct _zval_struct { =2E=2E=2E };
>typedef struct _zval_struct zval;
>```
>
>Some headers might want to forward declare zval so that zend_types=2Eh
>doesn't have to be included=2E The two primary reasons you might want to
>avoid that are 1=2E to reduce compile times if the header is very large
>and 2=2E to prevent recursive header dependencies=2E
>
>However, in C99 this code is actually illegal if both of these headers
>end up being included, because redeclarations of typedefs are not
>allowed=2E To fix it, the typedef must be removed and the signatures
>must refer to the struct directly=2E
>
>```c
>// some_header=2Eh
>struct _zval_struct;
>void some_func(struct _zval_struct *zv);
>```
>
>I started fixing these in a PR [1] which required more changes than
>expected=2E After a short discourse, we were wondering whether it might
>be better to switch to a newer C standard instead=2E Our coding
>standards [2] currently specify that compiling php-src requires C99=2E
>The Unix installation page on php=2Enet [3] claims it is ANSI C, which
>is certainly outdated=2E There have been suggestions to require C11 for
>a while, which should be well supported by all compilers shipped with
>maintained distributions=2E
>
>GCC gained support for C11 in 4=2E7 [4], LLVM Clang in 3=2E1, both
>released in 2012=2E For context, Debian Bullseye comes with GCC 10=2E2
>[5], Ubuntu Focal Fossa comes with GCC 9=2E3 [6], RHEL 8 comes with GCC
>8=2Ex [7]=2E=20
=20
Even Debian wheezy (out of extended LTS support) or Ubuntu 14=2E04 have GC=
C 4=2E7, so that seems OK=2E=20

How about Clang (for OSX) though? I can't check that easily=2E=20

cheers=20
Derick=20