Title: Macros
# 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 Utilties
`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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute) 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. 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-functions-that-behave-like-malloc)
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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#index-fallthrough-statement-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-Wformat-nonliteral-1) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-sentinel-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute)
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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005finstrument_005ffunction-function-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-may_005falias-type-attribute) 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](https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute)
and the [MSVC documentation](https://docs.microsoft.com/en-us/visualstudio/misc/inline-inline-forceinline)
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.