## Summary As of commit d2ea5bfb7a9c5df9601af71ccea4983a5fc9528b `Rts.h` attempts to use `static_assert()`: ```c +/* For _Static_assert */ +#include <assert.h> ... +#if __STDC_VERSION__ >= 201112L +#define GHC_STATIC_ASSERT(x, msg) static_assert((x), msg) +#else +#define GHC_STATIC_ASSERT(x, msg) +#endif ``` But in code generated from `derivedConstants` the order of `#include` files is: ``` #include "rts/PosixSource.h" #include "Rts.h" ... ``` which defines `_POSIX_SOURCE` on FreeBSD systems, which blocks the visibility of the C23 `static_assert()` (only the [C11 original](https://en.cppreference.com/w/c/language/_Static_assert) `_Static_assert()` is defined). The `<assert.h>` file on FreeBSD 12 reads in part: ```c /* * Static assertions. In principle we could define static_assert for * C++ older than C++11, but this breaks if _Static_assert is * implemented as a macro. * * C++ template parameters may contain commas, even if not enclosed in * parentheses, causing the _Static_assert macro to be invoked with more * than two parameters. */ #if __ISO_C_VISIBLE >= 2011 && !defined(__cplusplus) #define static_assert _Static_assert #endif ``` has `static_assert` conditional on `__ISO_C_VISIBLE`, and that macro is hidden when `_POSIX_SOURCE` is defined. From `<sys/cdefs.h>`: ```c #if defined(_POSIX_SOURCE) && !defined(_POSIX_C_SOURCE) # define _POSIX_C_SOURCE 198808 #endif #ifdef _POSIX_C_SOURCE # if _POSIX_C_SOURCE >= 200809 # define __POSIX_VISIBLE 200809 # define __ISO_C_VISIBLE 1999 # elif /* ... various older variants ... */ # ... # endif /* _POSIX_C_SOURCE */ #else /*- * Deal with _ANSI_SOURCE: ... */ # if defined(_ANSI_SOURCE) /* Hide almost everything. */ # define __POSIX_VISIBLE 0 # define __XSI_VISIBLE 0 # define __BSD_VISIBLE 0 # define __ISO_C_VISIBLE 1990 # define __EXT1_VISIBLE 0 # elif defined(_C99_SOURCE) /* Localism to specify strict C99 env. */ # define __POSIX_VISIBLE 0 # define __XSI_VISIBLE 0 # define __BSD_VISIBLE 0 # define __ISO_C_VISIBLE 1999 # define __EXT1_VISIBLE 0 # elif defined(_C11_SOURCE) /* Localism to specify strict C11 env. */ # define __POSIX_VISIBLE 0 # define __XSI_VISIBLE 0 # define __BSD_VISIBLE 0 # define __ISO_C_VISIBLE 2011 # define __EXT1_VISIBLE 0 # else /* Default environment: show everything. */ # define __POSIX_VISIBLE 200809 # define __XSI_VISIBLE 700 # define __BSD_VISIBLE 1 # define __ISO_C_VISIBLE 2011 # define __EXT1_VISIBLE 1 # endif #endif ``` Bottom line `__ISO_C_VISIBLE` is set to `2011` only if **none** of the various standards-compliance `_FOO_SOURCE` macros are defined. As a result the code generated by `deriveConstants` fails to compile: ``` Command line: .../deriveConstants --gen-header -o .../stage1/rts/build/include/DerivedConstants.h --tmpdir /tmp/extra-dir-51880349607072 --gcc-program /usr/local/bin/gcc10 --gcc-flag -Wall --gcc-flag -Werror=unused-but-set-variable --gcc-flag -Wno-error=inline --gcc-flag -Irts --gcc-flag -Irts/include --gcc-flag -I.../stage1/rts/build/include --gcc-flag -fcommon --nm-program /usr/local/bin/nm --objdump-program /usr/local/bin/objdump --target-os freebsd ===> Command failed with error code: 1 In file included from /tmp/extra-dir-51880349607072/tmp.c:14: rts/include/Rts.h:170:49: error: expected declaration specifiers or '...' before '(' token 170 | #define GHC_STATIC_ASSERT(x, msg) static_assert((x), msg) | ^ ``` Possible work-arounds: * Continue to use `_Static_assert`. * Include `<assert.h>` first. * Avoid the static assertion on FreeBSD 12 ## Steps to reproduce Attempt to build GHC 9.4.4 on FreeBSD 12.3. ## Expected behavior GHC 9.4.4 should build ## Environment * GHC version used: 9.4.4 Optional: * Operating System: FreeBSD 12.3 * System Architecture: x86_64