AN3350 datasheet(175/185 Pages) STMICROELECTRONICS

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AN3350

Pragmas for optimization

Doc ID 018512 Rev 2

175/185

Not all processors support misaligned accesses, which could cause a crash or incorrect

results. Even on processors which allow misaligned access, your program’s performance

might be reduced. Your program may have better performance if it treats the packed

structure as a byte stream, then packs and unpacks each byte from the stream.

Note:

Pragma pack is implemented somewhat differently by most compiler vendors, especially

when used with bitfields. If you need portability, you are probably better off using explicit shift

and mask operations in your program instead of bitfields.

22.16

strictheaderchecking

Controls how strict the compiler checks headers for standard C library functions.

Syntax

#pragma strictheaderchecking on | off | reset

Remarks

The 3.2 version compiler recognizes standard C library functions. If the correct prototype is

used, and, in C++, if the function appears in the “std” or root namespace, the compiler

recognizes the function, and is able to optimize calls to it based on its documented effects.

When this #pragma is on (default), in addition to having the correct prototype, the

declaration must also appear in the proper standard header file (and not in a user header or

source file).

This pragma does not correspond to any panel setting. By default, this pragma is on.

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