On 1 August 2024 22:57:36 BST, Ilija Tovilo <tovilo.il...@gmail.com> wrote:
>Hi everyone
>
>We've gotten a bug report about compile errors in the PHP 8.4 alpha on
>old C99 compilers (and on some modern compilers when passing the
>-std=c99 flag). Specifically, C99 does not support typedef
>redeclarations, which is a C11 feature.
>
>```c
>// some_header.h
>typedef struct _zval_struct zval;
>void some_func(zval *zv);
>
>// zend_types.h
>struct _zval_struct { ... };
>typedef struct _zval_struct zval;
>```
>
>Some headers might want to forward declare zval so that zend_types.h
>doesn't have to be included. The two primary reasons you might want to
>avoid that are 1. to reduce compile times if the header is very large
>and 2. to prevent recursive header dependencies.
>
>However, in C99 this code is actually illegal if both of these headers
>end up being included, because redeclarations of typedefs are not
>allowed. To fix it, the typedef must be removed and the signatures
>must refer to the struct directly.
>
>```c
>// some_header.h
>struct _zval_struct;
>void some_func(struct _zval_struct *zv);
>```
>
>I started fixing these in a PR [1] which required more changes than
>expected. After a short discourse, we were wondering whether it might
>be better to switch to a newer C standard instead. Our coding
>standards [2] currently specify that compiling php-src requires C99.
>The Unix installation page on php.net [3] claims it is ANSI C, which
>is certainly outdated. There have been suggestions to require C11 for
>a while, which should be well supported by all compilers shipped with
>maintained distributions.
>
>GCC gained support for C11 in 4.7 [4], LLVM Clang in 3.1, both
>released in 2012. For context, Debian Bullseye comes with GCC 10.2
>[5], Ubuntu Focal Fossa comes with GCC 9.3 [6], RHEL 8 comes with GCC
>8.x [7].
Even Debian wheezy (out of extended LTS support) or Ubuntu 14.04 have GCC 4.7,
so that seems OK.
How about Clang (for OSX) though? I can't check that easily.
cheers
Derick
