diff options
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/doc/extend.texi | 51 |
1 files changed, 32 insertions, 19 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index d2bf604..48c3aeb 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -2035,24 +2035,32 @@ called. Functions with these attributes are useful for initializing data that is used implicitly during the execution of the program. -On some targets the attributes also accept an integer argument to +On most targets the attributes also accept an integer argument to specify a priority to control the order in which constructor and -destructor functions are run. A constructor -with a smaller priority number runs before a constructor with a larger -priority number; the opposite relationship holds for destructors. Note -that priorities 0-100 are reserved. So, if you have a constructor that +destructor functions are run. The @var{priority} argument is a +constant integral expression bounded between 101 and 65535 inclusive; +priorities 0-100 are reserved for use by the compiler and its runtime +libraries. +A constructor with a smaller priority number runs before a constructor with +a larger priority number; the opposite relationship holds for destructors. +So, if you have a constructor that allocates a resource and a destructor that deallocates the same -resource, both functions typically have the same priority. The -priorities for constructor and destructor functions are the same as -those specified for namespace-scope C++ objects (@pxref{C++ Attributes}). -However, at present, the order in which constructors for C++ objects -with static storage duration and functions decorated with attribute -@code{constructor} are invoked is unspecified. In mixed declarations, -attribute @code{init_priority} can be used to impose a specific ordering. - -Using the argument forms of the @code{constructor} and @code{destructor} -attributes on targets where the feature is not supported is rejected with -an error. +resource, both functions typically have the same priority. + +The order in which constructors for C++ objects with static storage +duration are invoked relative to functions decorated with attribute +@code{constructor} is normally unspecified. You can use +attribute @code{init_priority} (@pxref{C++ Attributes}) on the +declarations of namespace-scope C++ objects to impose a specific +ordering; the @var{priority} for the @code{init_priority} attribute +has the same effect as the @var{priority} for the @code{constructor} +attribute. + +Using the argument form of the @code{constructor} and +@code{destructor} attributes on targets where the feature is not +supported is rejected with an error. Only a few targets (typically +those not using ELF object format, or the GNU linker) reject this +usage. @cindex @code{copy} function attribute @item copy @@ -30291,11 +30299,11 @@ variable or function or moving it into a tagged inline namespace. In Standard C++, objects defined at namespace scope are guaranteed to be initialized in an order in strict accordance with that of their definitions @emph{in a given translation unit}. No guarantee is made for initializations -across translation units. However, GNU C++ allows users to control the +across translation units. However, GNU C++ allows you to control the order of initialization of objects defined at namespace scope with the @code{init_priority} attribute by specifying a relative @var{priority}, -a constant integral expression currently bounded between 101 and 65535 -inclusive. Lower numbers indicate a higher priority. +with the same meaning as for the @code{constructor} attribute +(@pxref{Common Function Attributes}). In the following example, @code{A} would normally be created before @code{B}, but the @code{init_priority} attribute reverses that order: @@ -30309,6 +30317,11 @@ Some_Class B __attribute__ ((init_priority (543))); Note that the particular values of @var{priority} do not matter; only their relative ordering. +As with the @var{priority} argument to the @code{constructor} and +@code{destructor} attributes, a few targets do not support the +@code{init_priority} attribute. In that case the attribute is rejected +with an error rather than ignored. + @cindex @code{no_dangling} type attribute @cindex @code{no_dangling} function attribute @item no_dangling |