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libghostty: fix enum underlying type detection

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Use fixed int enum types for C++11, C23, Clang's fixed-enum extension, 
and GCC 13 or newer. Previously only finalized C23 mode selected an explicit 
underlying type, leaving C++ and common older C modes with 
implementation-defined enum types.
This commit is contained in:
Mitchell Hashimoto
2026-08-13 12:22:21 -07:00
parent 51992ab01a
commit e4ec4f0f95
1 changed files with 25 additions and 11 deletions
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36
include/ghostty/vt/types.h
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@@ -39,18 +39,21 @@
* The Zig side backs all C enums with c_int, so the C declarations
* must use int as their underlying type to maintain ABI compatibility.
*
* C23 (detected via __STDC_VERSION__ >= 202311L) supports explicit
* enum underlying types with `enum : int { ... }`. For pre-C23
* compilers, which are free to choose any type that can represent
* all values (C11 §6.7.2.2), we add an INT_MAX sentinel as the last
* entry to force the compiler to use int.
* C++11 and C23 support explicit enum underlying types with
* `enum : int { ... }`. Clang and GCC 13+ also support this syntax as
* an extension in older C language modes, so use it when available.
*
* Other pre-C23 C compilers are free to choose any type that can
* represent all values (C11 §6.7.2.2). For those compilers, we add an
* INT_MAX sentinel as the last entry so the compatible type must be
* able to represent INT_MAX. The exact compatible type and its
* signedness remain implementation-defined in this fallback.
*
* INT_MAX is used rather than a fixed constant like 0xFFFFFFFF
* because enum constants must have type int (which is signed).
* Values above INT_MAX overflow signed int and are a constraint
* violation in standard C; compilers that accept them interpret them
* as negative values via two's complement, which can collide with
* legitimate negative enum values.
* because enum constants must have type int in pre-C23 C. Values above
* INT_MAX are a constraint violation there; compilers that accept them
* may interpret them as negative values via two's complement, which can
* collide with legitimate negative enum values.
*
* Usage:
* @code
@@ -61,7 +64,18 @@
* } Foo;
* @endcode
*/
#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L
#if defined(__cplusplus) && \
(__cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1700))
#define GHOSTTY_ENUM_TYPED : int
#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L
#define GHOSTTY_ENUM_TYPED : int
#elif defined(__clang__)
#if __has_extension(c_fixed_enum)
#define GHOSTTY_ENUM_TYPED : int
#else
#define GHOSTTY_ENUM_TYPED
#endif
#elif defined(__GNUC__) && __GNUC__ >= 13
#define GHOSTTY_ENUM_TYPED : int
#else
#define GHOSTTY_ENUM_TYPED