5.2 Using Pragmas for Finer Control
For cases in which type-based analysis can benefit from more detail,
you can use the pragmas described in this section to override the alias level
in effect and specify the aliasing relationships between individual types
or pointer variables in the translation unit. These pragmas provide the most
benefit when the use of pointers in a translation unit is consistent with
one of the available alias levels while a few specific pointer variables are
used in an irregular way not allowed by one of the available levels.
Note - If you do not declare the named type or variable prior to the
pragma, a warning message is issued and the pragma is ignored. The results
of the program are undefined if the pragma appears after the first memory
reference to which its meaning applies.
The terms listed in the following table are used in the pragma definitions.
| |
|---|
level
|
|
type
| Any of the following: char, short, int, long, long long, float, double, long double
void, which denotes all pointer types
typedef name,
which is the name of a defined type from a typedef declaration
struct name,
which is the keyword struct followed by a struct tag name
union, which is the keyword union followed
by a union tag name
|
pointer_name
| The name of any variable of pointer type in the translation unit.
|
|