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| -rw-r--r-- | gcc/doc/extend.texi | 42 |
1 files changed, 31 insertions, 11 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index b83cd49..49df8e6 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -3488,17 +3488,37 @@ my_memcpy (void *dest, const void *src, size_t len) @end smallexample @noindent -causes the compiler to check that, in calls to @code{my_memcpy}, -arguments @var{dest} and @var{src} are non-null. If the compiler -determines that a null pointer is passed in an argument slot marked -as non-null, and the @option{-Wnonnull} option is enabled, a warning -is issued. @xref{Warning Options}. Unless disabled by -the @option{-fno-delete-null-pointer-checks} option the compiler may -also perform optimizations based on the knowledge that certain function -arguments cannot be null. In addition, -the @option{-fisolate-erroneous-paths-attribute} option can be specified -to have GCC transform calls with null arguments to non-null functions -into traps. @xref{Optimize Options}. +informs the compiler that, in calls to @code{my_memcpy}, arguments +@var{dest} and @var{src} must be non-null. + +The attribute has an effect both on functions calls and function definitions. + +For function calls: +@itemize @bullet +@item If the compiler determines that a null pointer is +passed in an argument slot marked as non-null, and the +@option{-Wnonnull} option is enabled, a warning is issued. +@xref{Warning Options}. +@item The @option{-fisolate-erroneous-paths-attribute} option can be +specified to have GCC transform calls with null arguments to non-null +functions into traps. @xref{Optimize Options}. +@item The compiler may also perform optimizations based on the +knowledge that certain function arguments cannot be null. These +optimizations can be disabled by the +@option{-fno-delete-null-pointer-checks} option. @xref{Optimize Options}. +@end itemize + +For function definitions: +@itemize @bullet +@item If the compiler determines that a function parameter that is +marked with nonnull is compared with null, and +@option{-Wnonnull-compare} option is enabled, a warning is issued. +@xref{Warning Options}. +@item The compiler may also perform optimizations based on the +knowledge that @code{nonnul} parameters cannot be null. This can +currently not be disabled other than by removing the nonnull +attribute. +@end itemize If no @var{arg-index} is given to the @code{nonnull} attribute, all pointer arguments are marked as non-null. To illustrate, the |