re PR other/56334 (__attribute__((aligned)) documentation is misleading)

2018-11-15  Sandra Loosemore  <sandra@codesourcery.com>

	PR other/56334

	gcc/
	* doc/extend.texi (Common Function Attributes): Clarify linker
	restrictions on "aligned" attribute.
	(Common Variable Attributes): Likewise.  Mention that linker
	restrictions don't apply to stack-allocated variables.

From-SVN: r266170

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3b42488c3ac0f9e2e22225e8969a6bf4e7b3242c..143a4398336ece00464ea9303c1d0a5a128d36c3 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2018-11-15  Sandra Loosemore  <sandra@codesourcery.com>
+
+       PR other/56334
+       * doc/extend.texi (Common Function Attributes): Clarify linker
+       restrictions on "aligned" attribute.
+       (Common Variable Attributes): Likewise.  Mention that linker
+       restrictions don't apply to stack-allocated variables.
+
 2018-11-15  Joern Rennecke  <joern.rennecke@riscy-ip.com>
 
        * gensupport.c (add_predicate_code): Properly handle ZERO_EXTRACT

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 15d973a7f48227d244e49206e73bfb3002e6755d..d4b1046b6ae5ce133ba38be761aab143492736c5 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -2396,7 +2396,8 @@ alignment this overrides the effect of the
 function.
 
 Note that the effectiveness of @code{aligned} attributes may be
-limited by inherent limitations in your linker.  On many systems, the
+limited by inherent limitations in the system linker 
+and/or object file format.  On some systems, the
 linker is only able to arrange for functions to be aligned up to a
 certain maximum alignment.  (For some linkers, the maximum supported
 alignment may be very very small.)  See your linker documentation for
@@ -6132,8 +6133,9 @@ attribute must be specified as well.  When used as part of a typedef, the
 @code{aligned} attribute can both increase and decrease alignment, and
 specifying the @code{packed} attribute generates a warning.
 
-Note that the effectiveness of @code{aligned} attributes may be limited
-by inherent limitations in your linker.  On many systems, the linker is
+Note that the effectiveness of @code{aligned} attributes for static
+variables may be limited by inherent limitations in the system linker
+and/or object file format.  On some systems, the linker is
 only able to arrange for variables to be aligned up to a certain maximum
 alignment.  (For some linkers, the maximum supported alignment may
 be very very small.)  If your linker is only able to align variables
@@ -6141,6 +6143,9 @@ up to a maximum of 8-byte alignment, then specifying @code{aligned(16)}
 in an @code{__attribute__} still only provides you with 8-byte
 alignment.  See your linker documentation for further information.
 
+Stack variables are not affected by linker restrictions; GCC can properly
+align them on any target.
+
 The @code{aligned} attribute can also be used for functions
 (@pxref{Common Function Attributes}.)