docs/toolchain-requirements.md - third_party/github.com/GNOME/glib - Git at Google

 Toolchain/Compiler requirements
 ===

 GLib requires a toolchain that supports C99.

 GLib contains some fall back code that allows supporting toolchains that are not
 fully C99-compatible.

 GLib makes some assumptions about features of the C library and C preprocessor,
 compiler and linker that may go beyond what C99 mandates.  We will use features
 beyond C99 if they are substantially useful and if they are supported in a wide
 range of compilers.

 In general, we are primarily interested in supporting these four compilers:

  * GCC on *nix
  * Clang (LLVM)
  * MSVC
  * mingw32-w64

 This is in keeping with our goal of primarily targetting GNU/Linux, Windows and
 Mac OS, along with Free Software POSIX-compliant operating systems.  See
 [Supported platforms](./supported-platforms.md) for a bit more information and
 rationale about that.

 In particular, we are interested in MSVC because, although there are other
 compilers which target Windows, they do not output debugging information that is
 compatible with MSVC.  In interest of usability, we want users of GLib to be
 able to debug GLib along with their own code while using MSVC as their
 development environment.

 At any given time, GLib may work with mingw32 (from mingw.org) but it is not
 specifically supported.  Politics aside, it seems that mingw.org is mostly
 dormant and, at this point, all of the big distributions have switched over to
 mingw32-w64.  In several cases, mingw.org has been missing APIs that we’ve
 wanted to use and upstream has not been responsive about adding them.

 GLib will attempt to remain compatible with other compilers, but some ‘extra
 features’ are assumed.  Those are detailed below.

 GLib additionally requires Python 3 to build.

 C99 Varargs macros
 ---

 _Hard requirement._

 GLib requires C99 ``__VA_ARG__`` support for both C and C++ compilers.

 Symbol visibility control
 ---

 _Not a hard requirement._

 When available, GLib uses `__attribute__((visibility("hidden")))` and the
 `-fvisibility=hidden` compiler option to control symbol visibility, and the
 `-Bsymbolic-functions` linker flag.

 Builtin atomic operations
 ---

 _Not a hard requirement._

 GLib will fall back to using a mutex-based implementation if atomic builtins are
 not available.

 C99 printf and positional parameters
 ---

 _Not a hard requirement._

 GLib can be built with an included printf implementation (from GNUlib) if the
 system printf is deficient.

 Constructors and destructors
 ---

 _Hard requirement._

 GLib can work with pragma-based, as well as with attribute-based constructor
 support. There is a fallback for MSVC using a `DllMain()` instead.

 `va_list` pass-by-reference
 ---

 _Hard requirement._

 GLib depends on the ability to pass-by-reference a `va_list`, as mandated in
 C99  § 7.15: “It is permitted to create a pointer to a `va_list` and pass that
 pointer to another function, in which case the original function may make
 further use of the original list after the other function returns.”

 Support for `static inline`
 ---

 _Hard requirement._

 GLib depends on implementation of the `inline` keyword as described by
 C99 § 6.7.4.

 GLib further assumes that functions appearing in header files and marked
 `static inline`, but not used in a particular compilation unit will:

  * not generate warnings about being unused
  * not be emitted in the compiler’s output

 It is possible that a compiler adheres to C99 § 6.7.4 but not to GLib’s further
 assumptions.  Such compilers may produce large numbers of warnings or large
 executables when compiling GLib or programs based on GLib.

 Support for `alloca()`
 ---

 _Hard requirement._

 Your compiler must support `alloca()`, defined in `<alloca.h>` (or `<malloc.h>`
 on Windows) and it must accept a non-constant argument.

 (C11) support for type redefinition
 ---

 **This requirement has been temporarily suspended (on account of OpenBSD
 carrying an old version of gcc) but it will probably return in the future.**

 Your compiler must allow “a typedef name [to] be redefined to denote the same
 type as it currently does”, as per C11 §6.7, item 3.

 ‘Big’ enums
 ---

 _Hard requirement._

 Some of our enum types use `1<<31` as a value. We also use negative values in
 enums. We rely on the compiler to choose a suitable storage size for the enum
 that can accommodate this.

 Selected C99 features
 ---

 _Hard requirement._

 Starting with GLib 2.52 and GTK+ 3.90, we will be using the following C99
 features where appropriate:

  * Compound literals
  * Designated initializers
  * Mixed declarations

 Function pointer conversions
 ---

 _Hard requirement._

 GLib heavily relies on the ability to convert a function pointer to a `void*`
 and back again losslessly. Any platform or compiler which doesn’t support this
 cannot be used to compile GLib or code which uses GLib. This precludes use of
 the `-pedantic` GCC flag with GLib.

 `stdint.h`
 ---

 _Hard requirement since GLib 2.67.x._

 GLib [requires a C99 `stdint.h`](https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1675)
 with all the usual sized integer types (`int8_t`, `uint64_t` and so on),
 believed to be supported by all relevant Unix platforms/compilers, as well as
 Microsoft compilers since MSVC 2013.
	Toolchain/Compiler requirements
	===

	GLib requires a toolchain that supports C99.

	GLib contains some fall back code that allows supporting toolchains that are not
	fully C99-compatible.

	GLib makes some assumptions about features of the C library and C preprocessor,
	compiler and linker that may go beyond what C99 mandates. We will use features
	beyond C99 if they are substantially useful and if they are supported in a wide
	range of compilers.

	In general, we are primarily interested in supporting these four compilers:

	* GCC on *nix
	* Clang (LLVM)
	* MSVC
	* mingw32-w64

	This is in keeping with our goal of primarily targetting GNU/Linux, Windows and
	Mac OS, along with Free Software POSIX-compliant operating systems. See
	[Supported platforms](./supported-platforms.md) for a bit more information and
	rationale about that.

	In particular, we are interested in MSVC because, although there are other
	compilers which target Windows, they do not output debugging information that is
	compatible with MSVC. In interest of usability, we want users of GLib to be
	able to debug GLib along with their own code while using MSVC as their
	development environment.

	At any given time, GLib may work with mingw32 (from mingw.org) but it is not
	specifically supported. Politics aside, it seems that mingw.org is mostly
	dormant and, at this point, all of the big distributions have switched over to
	mingw32-w64. In several cases, mingw.org has been missing APIs that we’ve
	wanted to use and upstream has not been responsive about adding them.

	GLib will attempt to remain compatible with other compilers, but some ‘extra
	features’ are assumed. Those are detailed below.

	GLib additionally requires Python 3 to build.

	C99 Varargs macros
	---

	_Hard requirement._

	GLib requires C99 ``__VA_ARG__`` support for both C and C++ compilers.

	Symbol visibility control
	---

	_Not a hard requirement._

	When available, GLib uses `__attribute__((visibility("hidden")))` and the
	`-fvisibility=hidden` compiler option to control symbol visibility, and the
	`-Bsymbolic-functions` linker flag.

	Builtin atomic operations
	---

	_Not a hard requirement._

	GLib will fall back to using a mutex-based implementation if atomic builtins are
	not available.

	C99 printf and positional parameters
	---

	_Not a hard requirement._

	GLib can be built with an included printf implementation (from GNUlib) if the
	system printf is deficient.

	Constructors and destructors
	---

	_Hard requirement._

	GLib can work with pragma-based, as well as with attribute-based constructor
	support. There is a fallback for MSVC using a `DllMain()` instead.

	`va_list` pass-by-reference
	---

	_Hard requirement._

	GLib depends on the ability to pass-by-reference a `va_list`, as mandated in
	C99 § 7.15: “It is permitted to create a pointer to a `va_list` and pass that
	pointer to another function, in which case the original function may make
	further use of the original list after the other function returns.”

	Support for `static inline`
	---

	_Hard requirement._

	GLib depends on implementation of the `inline` keyword as described by
	C99 § 6.7.4.

	GLib further assumes that functions appearing in header files and marked
	`static inline`, but not used in a particular compilation unit will:

	* not generate warnings about being unused
	* not be emitted in the compiler’s output

	It is possible that a compiler adheres to C99 § 6.7.4 but not to GLib’s further
	assumptions. Such compilers may produce large numbers of warnings or large
	executables when compiling GLib or programs based on GLib.

	Support for `alloca()`
	---

	_Hard requirement._

	Your compiler must support `alloca()`, defined in `<alloca.h>` (or `<malloc.h>`
	on Windows) and it must accept a non-constant argument.

	(C11) support for type redefinition
	---

	**This requirement has been temporarily suspended (on account of OpenBSD
	carrying an old version of gcc) but it will probably return in the future.**

	Your compiler must allow “a typedef name [to] be redefined to denote the same
	type as it currently does”, as per C11 §6.7, item 3.

	‘Big’ enums
	---

	_Hard requirement._

	Some of our enum types use `1<<31` as a value. We also use negative values in
	enums. We rely on the compiler to choose a suitable storage size for the enum
	that can accommodate this.

	Selected C99 features
	---

	_Hard requirement._

	Starting with GLib 2.52 and GTK+ 3.90, we will be using the following C99
	features where appropriate:

	* Compound literals
	* Designated initializers
	* Mixed declarations

	Function pointer conversions
	---

	_Hard requirement._

	GLib heavily relies on the ability to convert a function pointer to a `void*`
	and back again losslessly. Any platform or compiler which doesn’t support this
	cannot be used to compile GLib or code which uses GLib. This precludes use of
	the `-pedantic` GCC flag with GLib.

	`stdint.h`
	---

	_Hard requirement since GLib 2.67.x._

	GLib [requires a C99 `stdint.h`](https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1675)
	with all the usual sized integer types (`int8_t`, `uint64_t` and so on),
	believed to be supported by all relevant Unix platforms/compilers, as well as
	Microsoft compilers since MSVC 2013.