change precompile_headers to private to support build in cpp

[Ncerzzk]

How about chaning precompile_headers to private？

otherwise it would failed when using this lib in cpp project:(as the c99 grammers used in interface99 are not support by cpp, like restrict..etc)

/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: In function ‘Slice99 Slice99_empty(size_t)’:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:537:24: error: invalid conversion from ‘const void*’ to ‘void*’ [-fpermissive]
  537 |     return Slice99_new("", item_size, 0);
      |                        ^~
      |                        |
      |                        const void*
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:483:19: note:   initializing argument 1 of ‘Slice99 Slice99_new(void*, size_t, size_t)’
  483 | Slice99_new(void *ptr, size_t item_size, size_t len) {
      |             ~~~~~~^~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: At global scope:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:802:92: error: expected ‘,’ or ‘...’ before ‘backup’
  802 | inline static void Slice99_swap(Slice99 self, ptrdiff_t lhs, ptrdiff_t rhs, void *restrict backup) {
      |                                                                                            ^~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: In function ‘void Slice99_swap(Slice99, ptrdiff_t, ptrdiff_t, void*)’:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:803:5: error: ‘backup’ was not declared in this scope
  803 |     SLICE99_ASSERT(backup);
      |     ^~~~~~~~~~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: At global scope:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:823:88: error: expected ‘,’ or ‘...’ before ‘backup’
  823 | inline static void Slice99_swap_with_slice(Slice99 self, Slice99 other, void *restrict backup) {
      |                                                                                        ^~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: In function ‘void Slice99_swap_with_slice(Slice99, Slice99, void*)’:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:828:24: error: ‘backup’ was not declared in this scope
  828 |         SLICE99_MEMCPY(backup, Slice99_get(self, i), self.item_size);
      |                        ^~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: At global scope:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:843:65: error: expected ‘,’ or ‘...’ before ‘backup’
  843 | inline static void Slice99_reverse(Slice99 self, void *restrict backup) {
      |                                                                 ^~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: In function ‘void Slice99_reverse(Slice99, void*)’:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:844:5: error: ‘backup’ was not declared in this scope
  844 |     SLICE99_ASSERT(backup);
      |     ^~~~~~~~~~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: At global scope:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:865:60: error: expected ‘,’ or ‘...’ before ‘lhs’
  865 | Slice99_split_at(Slice99 self, size_t i, Slice99 *restrict lhs, Slice99 *restrict rhs) {
      |                                                            ^~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: In function ‘void Slice99_split_at(Slice99, size_t, Slice99*)’:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:867:5: error: ‘lhs’ was not declared in this scope
  867 |     SLICE99_ASSERT(lhs);
      |     ^~~~~~~~~~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:868:5: error: ‘rhs’ was not declared in this scope
  868 |     SLICE99_ASSERT(rhs);
      |     ^~~~~~~~~~~~~~
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: At global scope:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:885:58: error: ‘restrict’ was not declared in this scope; did you mean ‘struct’?
  885 | inline static char *Slice99_c_str(Slice99 self, char out[restrict]) {
      |                                                          ^~~~~~~~
      |                                                          struct
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h: In function ‘char* Slice99_c_str(...)’:
/home/radxa/rockchip_camera/build/_deps/slice99-src/slice99.h:886:5: error: ‘out’ was not declared in this scope
  886 |     SLICE99_ASSERT(out);
      |     ^~~~~~~~~~~~~~

and make the pre_compile headers to private could solve this problem.

[hirrolot]

as the c99 grammers used in interface99 are not support by cpp, like restrict..etc

Slice99 you mean. Interface99 doesn't use restrict :)

and make the pre_compile headers to private could solve this problem.

Are you sure that this will solve the problem? We also use a lot of C99 grammar in SmolRTSP itself. Have you tested the library with your fix on C++?

[Ncerzzk]

as the c99 grammers used in interface99 are not support by cpp, like restrict..etc

Slice99 you mean. Interface99 doesn't use restrict :)

and make the pre_compile headers to private could solve this problem.

Are you sure that this will solve the problem? We also use a lot of C99 grammar in SmolRTSP itself. Have you tested the library with your fix on C++?

Yes, I have test on my cpp project: https://github.com/Ncerzzk/rockchip_camera

Though with this fix, the cpp source file could not directly use this library too(once cpp source include the headers of this lib, compiler will complain about something relate to C99 grammar like the log above)

So I use this library in a C source file, and write a cpp wrapper to use it.

[hirrolot]

Thanks!