diff options
| -rw-r--r-- | gcc/doc/extend.texi | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 02578cd..0debf84 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -3240,7 +3240,9 @@ calls. Attribute @code{malloc} indicates that a function is @code{malloc}-like, i.e., that the pointer @var{P} returned by the function cannot alias any other pointer valid when the function returns, and moreover no -pointers to valid objects occur in any storage addressed by @var{P}. +pointers to valid objects occur in any storage addressed by @var{P}. In +addition, the GCC predicts that a function with the attribute returns +non-null in most cases. Independently, the form of the attribute with one or two arguments associates @code{deallocator} as a suitable deallocation function for @@ -3248,13 +3250,14 @@ pointers returned from the @code{malloc}-like function. @var{ptr-index} denotes the positional argument to which when the pointer is passed in calls to @code{deallocator} has the effect of deallocating it. -Using the attribute with no arguments is designed to improve optimization. -The compiler predicts that a function with the attribute returns non-null -in most cases. Functions like @code{malloc} and @code{calloc} have this -property because they return a pointer to uninitialized or zeroed-out -storage. However, functions like @code{realloc} do not have this property, -as they may return pointers to storage containing pointers to existing -objects. +Using the attribute with no arguments is designed to improve optimization +by relying on the aliasing property it implies. Functions like @code{malloc} +and @code{calloc} have this property because they return a pointer to +uninitialized or zeroed-out, newly obtained storage. However, functions +like @code{realloc} do not have this property, as they may return pointers +to storage containing pointers to existing objects. Additionally, since +all such functions are assumed to return null only infrequently, callers +can be optimized based on that assumption. Associating a function with a @var{deallocator} helps detect calls to mismatched allocation and deallocation functions and diagnose them under |