#pragma Preprocessor Directives |
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A pragma is an implementation-defined instruction to the compiler. It has the general form:
where character_sequence is a series of characters giving a specific compiler instruction and arguments, if any.
The character_sequence on a pragma is not subject to macro substitutions. More than one pragma construct can be specified on a single #pragma directive. The compiler ignores unrecognized pragmas.
Some #pragma directives, as indicated in the list below, must appear before any statements in the C source code. The other #pragma directives can be used throughout your program to affect a selected block of source code.
The C for AIX compiler lets you specify many compiler options as either command line options or as #pragma statements. In addition, the C for AIX compiler recognizes the pragmas listed below:
| Pragma Directive | Description |
| alloca | Provides an inline version of function alloca. This directive must appear before any statements in the C source code. |
| chars | Sets the sign type of character data. This directive must appear before any statements in the C source code. |
| comment | Places a comment into the object file. |
| disjoint | Lists identifiers not aliased to each other within the current scope of their use. |
| execution_frequency | Identifies the expected frequency with which a block of code will be executed. |
| hdrfile | Specifies the file name of the precompiled header to be generated and/or used. |
| hdrstop | Terminates the initial sequence of #include directives being considered for precompilation. |
| info | Controls the diagnostic messages generated by the -qinfo compiler option. |
| isolated_call | Lists functions that do not alter data objects visible at the time of the function call. |
| langlvl | Selects the C language level for compilation. This directive must appear before any statements in the C source code. |
| leaves | Specifies that a given function never returns. |
| map | Tells the compiler that all references to an identifier are to be converted to "name". |
| option_override | Lets you specify alternate optimization options for specific functions. |
| options | Specifies settings for compiler options in your source program. |
| reachable | Specifies that the point after a given routine, marked reachable, can be reached from a point other than the return from that routine. |
| strings | Sets storage type for strings. This directive must appear before any statements in the C source code. |
Note: The #pragma page, #pragma skip, #pragma subtitle, and #pragma title directives are not recognized by the C for AIX compiler.
Another set of pragma directives let you control parallel processing operations. See #pragma Preprocessor Directives for Parallel Processing for more information.
 Preprocessor Directives
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