AN3350 datasheet(166/185 Pages) STMICROELECTRONICS

166 / 185 page

Pragmas for code generation

AN3350

166/185

Doc ID 018512 Rev 2

Remarks

When this pragma is used, the optimizer can use the identifier errno (either a macro or a

function call) to optimize standard C library functions better. If not used, the optimizer makes

worst-case assumptions about the effects of calls to the standard C library.

Note:

The MSL C library already includes a use of this pragma, so you would only need to use it

for third-party C libraries.

If errno resolves to a variable name, specify it like this:

#pragma errno_name _Errno

If errno is a function call accessing ordinarily inaccessible global variables, use this form:

#pragma errno_name ...

Otherwise, do not use this pragma to prevent incorrect optimizations.

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

unspecified (worst case assumption).

21.5

explicit_zero_data

Controls the placement of zero-initialized data.

Syntax

#pragma explicit_zero_data on | off | reset

Remarks

Places zero-initialized data into the initialized data section instead of the BSS section when

By default, this pragma is off.

21.6

float_constants

Controls how floating pointing constants are treated.

Syntax

#pragma float_constants on | off | reset

Remarks

If you enable this pragma, the compiler assumes that all unqualified floating point constant

values are of type float, not double. This pragma is useful when porting source code for

programs optimized for the “float” rather than the “double” type.

When you enable this pragma, you can still explicitly declare a constant value as double by

appending a “D” suffix.

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

AN3350 Datasheet(PDF) 166 Page - STMicroelectronics