diff options
Diffstat (limited to 'gcc/doc/extend.texi')
| -rw-r--r-- | gcc/doc/extend.texi | 41 |
1 files changed, 5 insertions, 36 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index a119ad3..8c29e24 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -7138,11 +7138,9 @@ The @code{aligned} attribute can also be used for functions @cindex @code{counted_by} variable attribute @item counted_by (@var{count}) The @code{counted_by} attribute may be attached to the C99 flexible array -member, or a pointer field of a structure. It indicates that the number -of the elements of the array that is held by the flexible array member -field, or is pointed to by the pointer field, is given by the field -"@var{count}" in the same structure as the flexible array member or the -pointer field. +member of a structure. It indicates that the number of the elements of the +array is given by the field "@var{count}" in the same structure as the +flexible array member. This attribute is available only in C for now. In C++ this attribute is ignored. @@ -7163,22 +7161,8 @@ struct P @{ @end smallexample @noindent -specifies that the @code{array} is a flexible array member whose number -of elements is given by the field @code{count} in the same structure. - -@smallexample -struct PP @{ - size_t count2; - char other1; - char *array2 __attribute__ ((counted_by (count2))); - int other2; -@} *pp; -@end smallexample - -@noindent -specifies that the @code{array2} is an array that is pointed by the -pointer field, and its number of elements is given by the field -@code{count2} in the same structure. +specifies that the @code{array} is a flexible array member whose number of +elements is given by the field @code{count} in the same structure. The field that represents the number of the elements should have an integer type. Otherwise, the compiler reports an error and ignores @@ -7187,12 +7171,6 @@ the attribute. When the field that represents the number of the elements is assigned a negative integer value, the compiler treats the value as zero. -The @code{counted_by} attribute is not allowed for a pointer to @code{void}, -a pointer to function, or a pointer to a structure or union that includes -a flexible array member. However, it is allowed for a pointer to -non-void incomplete structure or union types, as long as the type could -be completed before the first reference to the pointer. - An explicit @code{counted_by} annotation defines a relationship between two objects, @code{p->array} and @code{p->count}, and there are the following requirements on the relationship between this pair: @@ -7208,13 +7186,6 @@ available all the time. This relationship must hold even after any of these related objects are updated during the program. @end itemize -In addition to the above requirements, there is one more requirement -between this pair if and only if @code{p->array} is an array that is -pointed by the pointer field: - -@code{p->array} and @code{p->count} can only be changed by changing the -whole structure at the same time. - It's the programmer's responsibility to make sure the above requirements to be kept all the time. Otherwise the compiler reports warnings and the results of the array bound sanitizer and the @@ -7236,8 +7207,6 @@ In the above, @code{ref1} uses @code{val1} as the number of the elements in @code{p->array}, and @code{ref2} uses @code{val2} as the number of elements in @code{p->array}. -Note, however, the above feature is not valid for the pointer field. - @cindex @code{alloc_size} variable attribute @item alloc_size (@var{position}) @itemx alloc_size (@var{position-1}, @var{position-2}) |