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feature_test_macros.7: Make text on required placement of macros more prominent 

Move the text that notes the requirement that feature test macros
must be defined before including any header files to the top of
the page, and highlight the text further, so that the reader will
not miss this point.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2010-09-10 07:15:16 +02:00
parent f8b212130c
commit e0530cbbdd
1 changed files with 8 additions and 7 deletions
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15
man7/feature_test_macros.7
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@ -33,6 +33,14 @@ feature_test_macros \- feature test macros
Feature test macros allow the programmer to control the definitions that
are exposed by system header files when a program is compiled.
.B NOTE:
In order to be effective, a feature test macro
.IR "must be defined before including any header files" .
This can either be done in the compilation command
.RI ( "cc \-DMACRO=value" )
or by defining the macro within the source code before
including any headers.
Some feature test macros are useful for creating portable applications,
by preventing nonstandard definitions from being exposed.
Other macros can be used to expose nonstandard definitions that
@ -41,13 +49,6 @@ The precise effects of each of the feature test macros described below
can be ascertained by inspecting the
.I <features.h>
header file.
In order to be effective, a feature test macro
.IR "must be defined before including any header files" .
This can either be done in the compilation command
.RI ( "cc \-DMACRO=value" )
or by defining the macro within the source code before
including any headers.
.SS Specification of feature test macro requirements in manual pages
When a function requires that a feature test macro is defined,
the manual page SYNOPSIS typically includes a note of the following form