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| author | Martin Sebor <msebor@redhat.com> | 2018-04-03 17:35:14 +0000 |
|---|---|---|
| committer | Martin Sebor <msebor@gcc.gnu.org> | 2018-04-03 11:35:14 -0600 |
| commit | b4231bf26e398d6799facf6bc93caeefd7d16d5a (patch) | |
| tree | 03cce51da066adc346384d5c7ba897532758fa49 /gcc | |
| parent | 92c59b7466a8caeab26f239ba4b004e68700d92e (diff) | |
| download | gcc-b4231bf26e398d6799facf6bc93caeefd7d16d5a.zip gcc-b4231bf26e398d6799facf6bc93caeefd7d16d5a.tar.gz gcc-b4231bf26e398d6799facf6bc93caeefd7d16d5a.tar.bz2 | |
extend.texi (Common Function Attributes): Clarify.
gcc/ChangeLog:
* doc/extend.texi (Common Function Attributes): Clarify.
(const attribute): Likewise.
(pure attribute): Likewise.
From-SVN: r259041
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/doc/extend.texi | 17 |
2 files changed, 18 insertions, 5 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index efd155e..82f6155 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2018-04-03 Martin Sebor <msebor@redhat.com> + + * doc/extend.texi (Common Function Attributes): Clarify. + (const attribute): Likewise. + (pure attribute): Likewise. + 2018-04-03 Jakub Jelinek <jakub@redhat.com> PR target/85169 diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index cb0d9c0..6296326 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -2275,8 +2275,11 @@ on a declaration, followed by an attribute specification inside double parentheses. You can specify multiple attributes in a declaration by separating them by commas within the double parentheses or by immediately following an attribute declaration with another attribute -declaration. @xref{Attribute Syntax}, for the exact rules on -attribute syntax and placement. +declaration. @xref{Attribute Syntax}, for the exact rules on attribute +syntax and placement. Compatible attribute specifications on distinct +declarations of the same function are merged. An attribute specification +that is not compatible with attributes already applied to a declaration +of the same function is ignored with a warning. GCC also supports attributes on variable declarations (@pxref{Variable Attributes}), @@ -2499,7 +2502,7 @@ themselves to optimization such as common subexpression elimination. The @code{const} attribute imposes greater restrictions on a function's definition than the similar @code{pure} attribute below because it prohibits the function from reading global variables. Consequently, the presence of -the attribute on a function declarations allows GCC to emit more efficient +the attribute on a function declaration allows GCC to emit more efficient code for some calls to the function. Decorating the same function with both the @code{const} and the @code{pure} attribute is diagnosed. @@ -2507,8 +2510,9 @@ both the @code{const} and the @code{pure} attribute is diagnosed. Note that a function that has pointer arguments and examines the data pointed to must @emph{not} be declared @code{const}. Likewise, a function that calls a non-@code{const} function usually must not be -@code{const}. It does not make sense for a @code{const} function to -return @code{void}. +@code{const}. Because a @code{const} function cannot have any side +effects it does not make sense for such a function to return @code{void}. +Declaring such a function is diagnosed. @item constructor @itemx destructor @@ -3218,6 +3222,9 @@ The @code{pure} attribute imposes similar but looser restrictions on a function's defintion than the @code{const} attribute: it allows the function to read global variables. Decorating the same function with both the @code{pure} and the @code{const} attribute is diagnosed. +Because a @code{pure} function cannot have any side effects it does not +make sense for such a function to return @code{void}. Declaring such +a function is diagnosed. @item returns_nonnull @cindex @code{returns_nonnull} function attribute |