Hi Gerald and Martin,
On Mon, Jan 28 2019, Gerald Pfeifer wrote:
> Hi Martin,
>
> On Sat, 26 Jan 2019, Martin Jambor wrote:
>>> What is a "wrong absolute value function"? That might be good to
>>> show by means of an example? (Also in invoke.texi, which I checked
>>> before writing this.)
>> I'm not sure how to change the wording, perhaps "...when a used absolute
>> value function seems wrong for the type of its argument" ...?
>
> yes, that definitely would have helped me as a user. (I guessed
> it might be that, but seeing it in writing helps.)
>
> On Mon, 28 Jan 2019, Martin Sebor wrote:
>> -Wabsolute-value warns for calls to standard functions that compute
>> the absolute value of an argument when a more appropriate standard
>> function is available. For example, calling abs(3.14) triggers
>> the warning because the appropriate function to call to compute
>> the absolute value of a double argument is fabs. The option also
>> triggers warnings when the argument in a call to such a function
>> has an unsigned type.
>
> Lovely.
>
> (I'd say "This option...", but that's probably a matter of taste.)
>
> Are you going to enhance both invoke.texi and apply a patch to the
> release notes (changes.html)? That would be ideal.
>
I have incorporated Martin's extended description to both invoke.texi
and changes.html, the result is in the two patches below. OK to commit
to trunk and to wwwdocs CVS repo respectively?
Thanks,
Martin
diff -u -r1.38 changes.html
--- htdocs/gcc-9/changes.html 7 Feb 2019 11:49:26 -0000 1.38
+++ htdocs/gcc-9/changes.html 13 Feb 2019 17:38:57 -0000
@@ -89,6 +89,23 @@
</ul></li>
</ul>
+<h3 id="c">C</h3>
+<ul>
+ <li>New warnings:
+ <ul>
+ <li><code>-Wabsolute-value</code> warns for calls to standard
+ functions that compute the absolute value of an argument when a
+ more appropriate standard function is available. For example,
+ calling <code>abs(3.14)</code> triggers the warning because the
+ appropriate function to call to compute the absolute value of a
+ double argument is <code>fabs</code>. The option also triggers
+ warnings when the argument in a call to such a function has an
+ unsigned type. This warning can be suppressed with an explicit
+ type cast and it is also enabled by <code>-Wextra</code>.
+ </li>
+ </ul></li>
+</ul>
+
<h3 id="cxx">C++</h3>
<ul>
<li>New warnings:
2019-02-13 Martin Jambor <mjam...@suse.cz>
Martin Sebor <mse...@redhat.com>
* doc/invoke.texi (Warning Options): Reword description of
-Wno-absolute-value.
---
gcc/doc/invoke.texi | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index c625350d04d..a8bafbebce8 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -6633,9 +6633,13 @@ example, warn if an unsigned variable is compared
against zero with
@item -Wabsolute-value @r{(C and Objective-C only)}
@opindex Wabsolute-value
@opindex Wno-absolute-value
-Warn when a wrong absolute value function seems to be used or when it
-does not have any effect because its argument is an unsigned type.
-This warning be suppressed with an explicit type cast and it is also
+Warn for calls to standard functions that compute the absolute value
+of an argument when a more appropriate standard function is available.
+For example, calling @code{abs(3.14)} triggers the warning because the
+appropriate function to call to compute the absolute value of a double
+argument is @code{fabs}. The option also triggers warnings when the
+argument in a call to such a function has an unsigned type. This
+warning can be suppressed with an explicit type cast and it is also
enabled by @option{-Wextra}.
@include cppwarnopts.texi
--
2.20.1
