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Compiler Attributes: improve explanation of header 

Explain better what "optional" attributes are, and avoid calling
them so to avoid confusion. Simply retain "Optional" as a word
to look for in the comments.

Moreover, add a couple sentences to explain a bit more the intention
and the documentation links.

Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
hifive-unleashed-5.1
Miguel Ojeda 2018-11-06 22:52:11 +01:00
parent 8bd66d147c
commit 24efee412c
1 changed files with 9 additions and 5 deletions
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14
include/linux/compiler_attributes.h
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@ -4,22 +4,26 @@
/*
* The attributes in this file are unconditionally defined and they directly
* map to compiler attribute(s) -- except those that are optional.
* map to compiler attribute(s), unless one of the compilers does not support
* the attribute. In that case, __has_attribute is used to check for support
* and the reason is stated in its comment ("Optional: ...").
*
* Any other "attributes" (i.e. those that depend on a configuration option,
* on a compiler, on an architecture, on plugins, on other attributes...)
* should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
* The intention is to keep this file as simple as possible, as well as
* compiler- and version-agnostic (e.g. avoiding GCC_VERSION checks).
*
* This file is meant to be sorted (by actual attribute name,
* not by #define identifier). Use the __attribute__((__name__)) syntax
* (i.e. with underscores) to avoid future collisions with other macros.
* If an attribute is optional, state the reason in the comment.
* Provide links to the documentation of each supported compiler, if it exists.
*/
/*
* To check for optional attributes, we use __has_attribute, which is supported
* on gcc >= 5, clang >= 2.9 and icc >= 17. In the meantime, to support
* 4.6 <= gcc < 5, we implement __has_attribute by hand.
* __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
* In the meantime, to support 4.6 <= gcc < 5, we implement __has_attribute
* by hand.
*
* sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
* depending on the compiler used to build it; however, these attributes have