#### Macros

GLib provides a set of C pre-processor macros and symbols for commonly-used language and platform features.

## Platform

`G_OS_WIN32`
  This macro is defined only on Windows, so you can bracket Windows-specific code using `#ifdef G_OS_WIN32 ... #endif`.
`G_OS_UNIX`

  This macro is defined only on UNIX and UNIX-like systems, so you can bracket UNIX-specific code in `#ifdef G_OS_UNIX ... #endif`. To detect whether to compile features that require a specific kernel or operating system, check for the appropriate OS-specific predefined macros instead, for example:

  - Linux kernel (any libc, including glibc, musl or Android): `#ifdef __linux__`
  - Linux kernel and GNU user-space: `#if defined(__linux__) && defined(__GLIBC__)`
  - FreeBSD kernel (any libc, including glibc): `#ifdef __FreeBSD_kernel__`
  - FreeBSD kernel and user-space: `#ifdef __FreeBSD__`
  - Apple operating systems (macOS, iOS, tvOS), regardless of whether Cocoa/Carbon toolkits are available: `#ifdef __APPLE__`

  See https://sourceforge.net/p/predef/wiki/OperatingSystems/ for more.

`G_DIR_SEPARATOR`
  The directory separator character. This is `'/'` on UNIX machines and `'\'` under Windows.
`G_DIR_SEPARATOR_S`
  The directory separator as a string. This is `"/"` on UNIX machines and `"\"` under Windows.
`G_IS_DIR_SEPARATOR(ch)`
  Checks whether a character is a directory separator. It returns true for `'/'` on UNIX machines and for `'\'` or `'/'` under Windows. Available since 2.6.
`G_SEARCHPATH_SEPARATOR`
  The search path separator character. This is `':'` on UNIX machines and `';'` under Windows.
`G_SEARCHPATH_SEPARATOR_S`
  The search path separator as a string. This is `":"` on UNIX machines and `";"` under Windows.

## Values

`TRUE`
  Defines the true value for the `gboolean` type.
`FALSE`
  Defines the false value for the `gboolean` type.
`NULL`
  Defines the standard `NULL` pointer.

## Maths

`MIN(a, b)`
  Calculates the minimum of `a` and `b`.
`MAX(a, b)`
  Calculates the maximum of `a` and `b`.
`ABS(value)`

  Calculates the absolute value of a given numerical value. The absolute value is simply the number with any negative sign taken away.

  For example,

  - `ABS(-10)` is 10.
  - `ABS(10)` is also 10.
`CLAMP(value, low, high)`

  Ensures that a value is between the limits set by `low` and `high`. If `low` is greater than `high` the result is undefined.

  For example,

  - `CLAMP(5, 10, 15)` is 10.
  - `CLAMP(15, 5, 10)` is 10.
  - `CLAMP(20, 15, 25)` is 20.
`G_APPROX_VALUE(a, b, epsilon)`

  Evaluates to true if the absolute difference between the given numerical values `a` and `b` is smaller than `epsilon`, and to false otherwise.

  For example,

  - `G_APPROX_VALUE (5, 6, 2)` evaluates to true
  - `G_APPROX_VALUE (3.14, 3.15, 0.001)` evaluates to false
  - `G_APPROX_VALUE (n, 0.f, FLT_EPSILON)` evaluates to true if `n` is within the single precision floating point epsilon from zero

  Available since: 2.58

## Structure Access

`G_STRUCT_MEMBER(member_type, struct_pointer, offset)`
  Returns a member of a structure at a given offset, using the given type.
`G_STRUCT_MEMBER_P(struct_pointer, offset)`
  Returns an untyped pointer to a given offset of a struct.
`G_STRUCT_OFFSET(struct_type, member_name)`
  Returns the offset, in bytes, of a member of a struct. Consider using standard C `offsetof()`, available since at least C89 and C++98, in new code (but note that `offsetof()` returns a `size_t` rather than a `long`).

## Array Utilities

`G_N_ELEMENTS(array)`
  Determines the number of elements in an array. The array must be declared so the compiler knows its size at compile-time; this macro will not work on an array allocated on the heap, only static arrays or arrays on the stack.

## Miscellaneous Macros

These macros provide more specialized features which are not needed so often by application programmers.

`G_STMT_START`
  Starts a multi-statement macro block so that it can be used in places where only one statement is expected by the compiler.
`G_STMT_END`
  Ends a multi-statement macro block so that it can be used in places where only one statement is expected by the compiler.
`G_BEGIN_DECLS`
  Used (along with `G_END_DECLS`) to bracket C header files that may be included by C++ sources. If the compiler in use is a C++ compiler, starts an `extern "C"` around the header.
`G_END_DECLS`
  Used (along with `G_BEGIN_DECLS`) to bracket C header files that may be included by C++ sources, or compiled by a C++ compiler. If the compiler in use is a C++ compiler, ends the `extern "C"` block around the header.
`G_VA_COPY(ap1, ap2)`

  Portable way to copy `va_list` variables.

  In order to use this function, you must include `string.h` yourself, because this macro may use `memmove()` and GLib does not include `string.h` for you.

  Each invocation of `G_VA_COPY (ap1, ap2)` must be matched with a corresponding `va_end (ap1)` call in the same function.

  This is equivalent to standard C `va_copy()`, available since C99 and C++11, which should be preferred in new code.

`G_STRINGIFY(macro_or_string)`

  Accepts a macro or a string and converts it into a string after preprocessor argument expansion. For example, the following code:

      #define AGE 27
      const gchar *greeting = G_STRINGIFY (AGE) " today!";

  is transformed by the preprocessor into (code equivalent to):

      const gchar *greeting = "27 today!";

`G_PASTE(identifier1, identifier2)`

  Yields a new preprocessor pasted identifier `identifier1identifier2` from its expanded arguments `identifier1` and `identifier2`. For example,the following code:

      #define GET(traveller,method) G_PASTE(traveller_get_, method) (traveller)
      const char *name = GET (traveller, name);
      const char *quest = GET (traveller, quest);
      Color *favourite = GET (traveller, favourite_colour);

  is transformed by the preprocessor into:

      const char *name = traveller_get_name (traveller);
      const char *quest = traveller_get_quest (traveller);
      Color *favourite = traveller_get_favourite_colour (traveller);

  Available since: 2.20

`G_STATIC_ASSERT(expr)`

  The `G_STATIC_ASSERT()` macro lets the programmer check a condition at compile time. The condition needs to be compile time computable. The macro can be used in any place where a `typedef` is valid.

  A `typedef` is generally allowed in exactly the same places that a variable declaration is allowed. For this reason, you should not use `G_STATIC_ASSERT()` in the middle of blocks of code.

  The macro should only be used once per source code line.

  Since: 2.20

`G_STATIC_ASSERT_EXPR(expr)`

  The `G_STATIC_ASSERT_EXPR()` macro lets the programmer check a condition at compile time. The condition needs to be compile time computable.

  Unlike `G_STATIC_ASSERT()`, this macro evaluates to an expression and, as such, can be used in the middle of other expressions. Its value should be ignored. This can be accomplished by placing it as the first argument of a comma expression.

      #define ADD_ONE_TO_INT(x) \
        (G_STATIC_ASSERT_EXPR(sizeof (x) == sizeof (int)), ((x) + 1))

  Since: 2.30

## Compiler

`G_GNUC_EXTENSION`
  Expands to `__extension__` when GCC is used as the compiler. This simply tells GCC not to warn about the following non-standard code when compiling with the `-pedantic` option.
`G_GNUC_CONST`

  Expands to the GNU C `const` function attribute if the compiler is GCC. Declaring a function as `const` enables better optimization of calls to the function. A `const` function doesn’t examine any values except its parameters, and has no effects except its return value.

  Place the attribute after the declaration, just before the semicolon.

      gchar g_ascii_tolower (gchar c) G_GNUC_CONST;

  See the GNU C documentation for more details.

  A function that has pointer arguments and examines the data pointed to must not be declared `const`. Likewise, a function that calls a non-`const` function usually must not be `const`. It doesn’t make sense for a `const` function to return `void`.

`G_GNUC_PURE`

  Expands to the GNU C `pure` function attribute if the compiler is GCC. Declaring a function as `pure` enables better optimization of calls to the function. A `pure` function has no effects except its return value and the return value depends only on the parameters and/or global variables.

  Place the attribute after the declaration, just before the semicolon.

      gboolean g_type_check_value (const GValue *value) G_GNUC_PURE;

  See the GNU C documentation for more details.

`G_GNUC_UNUSED`

  Expands to the GNU C `unused` function attribute if the compiler is gcc. It is used for declaring functions and arguments which may never be used. It avoids possible compiler warnings.

  For functions, place the attribute after the declaration, just before the semicolon. It cannot go in the definition of a function, only the declaration. For arguments, place the attribute at the beginning of the argument declaration.

      void my_unused_function (G_GNUC_UNUSED gint unused_argument,
                               gint other_argument) G_GNUC_UNUSED;

  See the GNU C documentation for more details.

`G_GNUC_MALLOC`

  Expands to the GNU C `malloc` function attribute if the compiler is GCC.

  Declaring a function as `malloc` enables better optimization of the function, but must only be done if the allocation behaviour of the function is fully understood, otherwise miscompilation can result.

  A function can have the `malloc` attribute if it returns a pointer which is guaranteed to not alias with any other pointer valid when the function returns, and moreover no pointers to valid objects occur in any storage addressed by the returned pointer.

  In practice, this means that `G_GNUC_MALLOC` can be used with any function which returns unallocated or zeroed-out memory, but not with functions which return initialised structures containing other pointers, or with functions that reallocate memory. This definition changed in GLib 2.58 to match the stricter definition introduced around GCC 5.

  Place the attribute after the declaration, just before the semicolon.

      gpointer g_malloc (gsize n_bytes) G_GNUC_MALLOC G_GNUC_ALLOC_SIZE(1);

  See the GNU C documentation for more details.

  Since: 2.6

`G_GNUC_DEPRECATED`

  Expands to the GNU C `deprecated` attribute if the compiler is GCC. It can be used to mark `typedef`s, variables and functions as deprecated. When called with the `-Wdeprecated-declarations` option, gcc will generate warnings when deprecated interfaces are used.

  Place the attribute after the declaration, just before the semicolon.

      int my_mistake (void) G_GNUC_DEPRECATED;

  See the GNU C documentation for more details.

  See also: `G_DEPRECATED`

  Since: 2.2

`G_GNUC_DEPRECATED_FOR(func)`

  Like `G_GNUC_DEPRECATED`, but names the intended replacement for the deprecated symbol if the version of gcc in use is new enough to support custom deprecation messages.

  Place the attribute after the declaration, just before the semicolon.

      int my_mistake (void) G_GNUC_DEPRECATED_FOR(my_replacement);

  See the GNU C documentation for more details.

  Note that if `func` is a macro, it will be expanded in the warning message. You can enclose it in quotes to prevent this. (The quotes will show up in the warning, but it’s better than showing the macro expansion.)

  Since: 2.26

`G_GNUC_NORETURN`

  Expands to the GNU C `noreturn` function attribute if the compiler is GCC. It is used for declaring functions which never return. It enables optimization of the function, and avoids possible compiler warnings.

  Since 2.68, it is recommended that code uses `G_NORETURN` instead of `G_GNUC_NORETURN`, as that works on more platforms and compilers (in particular, MSVC and C++11) than `G_GNUC_NORETURN`, which works with GCC and Clang only. `G_GNUC_NORETURN` continues to work, so has not been deprecated yet.

  Place the attribute after the declaration, just before the semicolon.

      void g_abort (void) G_GNUC_NORETURN;

  See the GNU C documentation for more details.

`G_GNUC_FALLTHROUGH`

  Expands to the GNU C `fallthrough` statement attribute if the compiler supports it. This allows declaring case statement to explicitly fall through in switch statements. To enable this feature, use `-Wimplicit-fallthrough` during compilation.

  Put the attribute right before the case statement you want to fall through to.

      switch (foo)
        {
        case 1:
          g_message ("it's 1");
          G_GNUC_FALLTHROUGH;
        case 2:
          g_message ("it's either 1 or 2");
          break;
        }

  See the GNU C documentation for more details.

  Since: 2.60

`G_GNUC_FORMAT(idx)`

  Expands to the GNU C `format_arg` function attribute if the compiler is GCC. This function attribute specifies that a function takes a format string for a `printf()`, `scanf()`, `strftime()` or `strfmon()` style function and modifies it, so that the result can be passed to a `printf()`, `scanf()`, `strftime()` or `strfmon()` style function (with the remaining arguments to the format function the same as they would have been for the unmodified string).

  Place the attribute after the function declaration, just before the semicolon.

      gchar *g_dgettext (gchar *domain_name, gchar *msgid) G_GNUC_FORMAT (2);

  See the GNU C documentation for more details.

`G_GNUC_NULL_TERMINATED`

  Expands to the GNU C `sentinel` function attribute if the compiler is GCC. This function attribute only applies to variadic functions and instructs the compiler to check that the argument list is terminated with an explicit `NULL`.

  Place the attribute after the declaration, just before the semicolon.

      gchar *g_strconcat (const gchar *string1,
                          ...) G_GNUC_NULL_TERMINATED;

  See the GNU C documentation for more details

  Since: 2.8

`G_GNUC_WARN_UNUSED_RESULT`

  Expands to the GNU C `warn_unused_result` function attribute if the compiler is GCC. This function attribute makes the compiler emit a warning if the result of a function call is ignored.

  Place the attribute after the declaration, just before the semicolon.

      GList *g_list_append (GList *list,
                            gpointer data) G_GNUC_WARN_UNUSED_RESULT;

  See the GNU C documentation for more details.

  Since: 2.10

`G_GNUC_NO_INLINE`

  Expands to the GNU C `noinline` function attribute if the compiler is GCC.

  Declaring a function as `noinline` prevents the function from being considered for inlining.

  This macro is provided for retro-compatibility and will be eventually deprecated; `G_NO_INLINE` should be used instead.

  The attribute may be placed before the declaration or definition, right before the `static` keyword.

      G_GNUC_NO_INLINE
      static int
      do_not_inline_this (void)
      {
      // ...
      }

  See the GNU C documentation for more details.

  See also: `G_NO_INLINE`, `G_ALWAYS_INLINE`.

  Since: 2.58

`G_GNUC_NO_INSTRUMENT`

  Expands to the GNU C `no_instrument_function` function attribute if the compiler is GCC. Functions with this attribute will not be instrumented for profiling, when the compiler is called with the `-finstrument-functions` option.

  Place the attribute after the declaration, just before the semicolon.

      int do_uninteresting_things (void) G_GNUC_NO_INSTRUMENT;

  See the GNU C documentation for more details.

`G_GNUC_MAY_ALIAS`

  Expands to the GNU C `may_alias` type attribute if the compiler is GCC. Types with this attribute will not be subjected to type-based alias analysis, but are assumed to alias with any other type, just like `char`.

  See the GNU C documentation for details.

  Since: 2.14

`G_GNUC_FUNCTION`

  Expands to `""` on all modern compilers, and to `__FUNCTION__` on GCC version 2.x. Don’t use it.

  Deprecated: 2.16: Use `G_STRFUNC()` instead

`G_GNUC_PRETTY_FUNCTION`

  Expands to `""` on all modern compilers, and to `__PRETTY_FUNCTION__` on GCC version 2.x. Don’t use it.

  Deprecated: 2.16: Use `G_STRFUNC()` instead

`G_GNUC_CHECK_VERSION(major, minor)`

  Expands to a check for a compiler with `__GNUC__` defined and a version greater than or equal to the major and minor numbers provided. For example, the following would only match on compilers such as GCC 4.8 or newer.

      #if G_GNUC_CHECK_VERSION(4, 8)
      // ...
      #endif

  Since: 2.42

`G_GNUC_BEGIN_IGNORE_DEPRECATIONS`

  Tells GCC (if it is a new enough version) to temporarily stop emitting warnings when functions marked with `G_GNUC_DEPRECATED` or `G_GNUC_DEPRECATED_FOR` are called. This is useful for when you have one deprecated function calling another one, or when you still have regression tests for deprecated functions.

  Use `G_GNUC_END_IGNORE_DEPRECATIONS` to resume warning again. (If you are not compiling with `-Wdeprecated-declarations` then neither macro has any effect.)

  This macro can be used either inside or outside of a function body, but must appear on a line by itself.

      static void
      test_deprecated_function (void)
      {
        G_GNUC_BEGIN_IGNORE_DEPRECATIONS
        g_assert_cmpint (my_mistake (), ==, 42);
        G_GNUC_END_IGNORE_DEPRECATIONS
      }

  Both this macro and the corresponding `G_GNUC_END_IGNORE_DEPRECATIONS` are considered statements, so they should not be used around branching or loop conditions; for instance, this use is invalid:

      G_GNUC_BEGIN_IGNORE_DEPRECATIONS
      if (check == some_deprecated_function ())
      G_GNUC_END_IGNORE_DEPRECATIONS
        {
          do_something ();
        }

  and you should move the deprecated section outside the condition

      // Solution A
      some_data_t *res;

      G_GNUC_BEGIN_IGNORE_DEPRECATIONS
      res = some_deprecated_function ();
      G_GNUC_END_IGNORE_DEPRECATIONS

      if (check == res)
        {
          do_something ();
        }

      // Solution B
      G_GNUC_BEGIN_IGNORE_DEPRECATIONS
      if (check == some_deprecated_function ())
        {
          do_something ();
        }
      G_GNUC_END_IGNORE_DEPRECATIONS

  Since: 2.32

`G_GNUC_END_IGNORE_DEPRECATIONS`

  Undoes the effect of `G_GNUC_BEGIN_IGNORE_DEPRECATIONS`, telling GCC to resume outputting warnings again (assuming those warnings had been enabled to begin with).

  This macro can be used either inside or outside of a function body, but must appear on a line by itself.

  Since: 2.32

`G_C_STD_VERSION`

  The C standard version the code is compiling against, it’s normally defined with the same value of `__STDC_VERSION__` for C standard compatible compilers, while it uses the lowest standard version in pure MSVC, given that in such compiler the definition depends on a compilation flag.

  This is granted to be undefined when compiling with a C++ compiler.

  See also: `G_C_STD_CHECK_VERSION` and `G_CXX_STD_VERSION`

  Since: 2.76

`G_C_STD_CHECK_VERSION(version)`

  Macro to check if the current compiler supports a specified version of the C standard. Such value must be numeric and can be provided both in the short form for the well-known versions (e.g. `90`, `99`…) or in the complete form otherwise (e.g. `199000L`, `199901L`, `205503L`…).

  When a C++ compiler is used, the macro is defined and evaluates to false.

  This value is compared against `G_C_STD_VERSION`.

      #if G_C_STD_CHECK_VERSION(17)
      // ...
      #endif

  See also: `G_CXX_STD_CHECK_VERSION`

  Since: 2.76

`G_CXX_STD_VERSION`

  The C++ standard version the code is compiling against, it’s defined with the same value of `__cplusplus` for C++ standard compatible compilers, while it uses `_MSVC_LANG` in MSVC, given that the standard definition depends on a compilation flag in such compiler.

  This is granted to be undefined when not compiling with a C++ compiler.

  See also: `G_CXX_STD_CHECK_VERSION` and `G_C_STD_VERSION`

  Since: 2.76

`G_CXX_STD_CHECK_VERSION(version)`

  Macro to check if the current compiler supports a specified `version` of the C++ standard. Such value must be numeric and can be provided both in the short form for the well-known versions (e.g. `11`, `17`…) or in the complete form otherwise (e.g. `201103L`, `201703L`, `205503L`…).

  When a C compiler is used, the macro evaluates to false.

  This value is compared against `G_CXX_STD_VERSION`.

      #if G_CXX_STD_CHECK_VERSION(20)
      // ...
      #endif

  See also: `G_C_STD_CHECK_VERSION`

  Since: 2.76

`G_LIKELY(expr)`

  Hints the compiler that the expression is likely to evaluate to a true value. The compiler may use this information for optimizations.

      if (G_LIKELY (random () != 1))
        g_print ("not one");

  Since: 2.2

`G_UNLIKELY(expr)`

  Hints the compiler that the expression is unlikely to evaluate to a true value. The compiler may use this information for optimizations.

      if (G_UNLIKELY (random () == 1))
        g_print ("a random one");

  Since: 2.2

`G_ALIGNOF(type)`

  Evaluates to the minimal alignment required by the platform ABI for values of the given type. The address of a variable or struct member of the given type must always be a multiple of this alignment. For example, most platforms require int variables to be aligned at a 4-byte boundary, so `G_ALIGNOF (int)` is 4 on most platforms.

  Note this is not necessarily the same as the value returned by GCC’s `__alignof__` operator, which returns the preferred alignment for a type. The preferred alignment may be a stricter alignment than the minimal alignment.

  Since: 2.60

`G_SIZEOF_MEMBER(struct_type, member_name)`

  Evaluates to the size in bytes of `member_name` in the struct definition without having a declared instance of `struct_type`.

  Since: 2.64

`G_NORETURN`

  Expands to the GNU C or MSVC `noreturn` function attribute depending on the compiler. It is used for declaring functions which never return. Enables optimization of the function, and avoids possible compiler warnings.

  Note that `G_NORETURN` supersedes the previous `G_GNUC_NORETURN` macro, which will eventually be deprecated. `G_NORETURN` supports more platforms.

  Place the attribute before the function declaration as follows:

      G_NORETURN void g_abort (void);

  Since: 2.68

`G_NORETURN_FUNCPTR`

  Expands to the GNU C or MSVC `noreturn` function attribute depending on the compiler. It is used for declaring function pointers which never return. Enables optimization of the function, and avoids possible compiler warnings.

  Place the attribute before the function declaration as follows:

      G_NORETURN_FUNCPTR void (*funcptr) (void);

  Note that if the function is not a function pointer, you can simply use the `G_NORETURN` macro as follows:

      G_NORETURN void g_abort (void);

  Since: 2.68

`G_ALWAYS_INLINE`

  Expands to the GNU C `always_inline` or MSVC `__forceinline` function attribute depending on the compiler. It is used for declaring functions as always inlined, ignoring the compiler optimization levels.

  The attribute may be placed before the declaration or definition, right before the `static` keyword.

      G_ALWAYS_INLINE
      static int
      do_inline_this (void)
      {
      // ...
      }

  See the GNU C documentation and the MSVC documentation for more details.

  Since: 2.74

`G_NO_INLINE`

  Expands to the GNU C or MSVC `noinline` function attribute depending on the compiler. It is used for declaring functions preventing from being considered for inlining.

  Note that `G_NO_INLINE` supersedes the previous `G_GNUC_NO_INLINE` macro, which will eventually be deprecated. `G_NO_INLINE` supports more platforms.

  The attribute may be placed before the declaration or definition, right before the `static` keyword.

      G_NO_INLINE
      static int
      do_not_inline_this (void)
      {
      // ...
      }

  Since: 2.74

`G_STRLOC`
  Expands to a string identifying the current code position.
`G_STRFUNC`
  Expands to a string identifying the current function. Since: 2.4
`G_GNUC_INTERNAL`

  This attribute can be used for marking library functions as being used internally to the library only, which may allow the compiler to handle function calls more efficiently. Note that static functions do not need to be marked as internal in this way. See the GNU C documentation for details.

  When using a compiler that supports the GNU C hidden visibility attribute, this macro expands to `__attribute__((visibility("hidden")))`. When using the Sun Studio compiler, it expands to `__hidden`.

  Note that for portability, the attribute should be placed before the function declaration. While GCC allows the macro after the declaration, Sun Studio does not.

      G_GNUC_INTERNAL
      void _g_log_fallback_handler (const gchar    *log_domain,
                                    GLogLevelFlags  log_level,
                                    const gchar    *message,
                                    gpointer        unused_data);

  Since: 2.6

`G_HAVE_GNUC_VISIBILITY`
  Defined to 1 if GCC-style visibility handling is supported.

## Deprecation

`G_DEPRECATED`

  This macro is similar to `G_GNUC_DEPRECATED`, and can be used to mark functions declarations as deprecated. Unlike `G_GNUC_DEPRECATED`, it is meant to be portable across different compilers and must be placed before the function declaration.

      G_DEPRECATED
      int my_mistake (void);

  Since: 2.32

`G_DEPRECATED_FOR(f)`

  This macro is similar to `G_GNUC_DEPRECATED_FOR`, and can be used to mark functions declarations as deprecated. Unlike `G_GNUC_DEPRECATED_FOR`, it is meant to be portable across different compilers and must be placed before the function declaration.

      G_DEPRECATED_FOR(my_replacement)
      int my_mistake (void);

  Since: 2.32

`G_UNAVAILABLE(major, minor)`

  This macro can be used to mark a function declaration as unavailable. It must be placed before the function declaration. Use of a function that has been annotated with this macros will produce a compiler warning.

  Since: 2.32

`GLIB_DISABLE_DEPRECATION_WARNINGS`
  A macro that should be defined before including the `glib.h` header. If it is defined, no compiler warnings will be produced for uses of deprecated GLib APIs.

## Version checking

`GLIB_MAJOR_VERSION`

  A macro that evaluates to the major component of the version of GLib, e.g. `1` for version `1.2.3`.

`GLIB_MINOR_VERSION`

  A macro that evaluates to the minor component of the version of GLib, e.g. `2` for version `1.2.3`.

`GLIB_MICRO_VERSION`

  A macro that evaluates to the micro component of the version of GLib, e.g. `3` for version `1.2.3`.

`GLIB_CHECK_VERSION (major, minor, micro)`

  A macro that evaluates to true if the version of GLib is newer than the given version tuple.