[gentoo-doc-cvs] cvs commit: gcc-optimization.xml

[Josh Saddler]

nightmorph    07/07/29 06:58:08

  Modified:             gcc-optimization.xml
  Log:
  changed Os stuff and backtraces, bug 186891

Revision  Changes    Path
1.7                  xml/htdocs/doc/en/gcc-optimization.xml

file : http://sources.gentoo.org/viewcvs.py/gentoo/xml/htdocs/doc/en/gcc-optimization.xml?rev=1.7&view=markup
plain: http://sources.gentoo.org/viewcvs.py/gentoo/xml/htdocs/doc/en/gcc-optimization.xml?rev=1.7&content-type=text/plain
diff : http://sources.gentoo.org/viewcvs.py/gentoo/xml/htdocs/doc/en/gcc-optimization.xml?r1=1.6&r2=1.7

Index: gcc-optimization.xml
===================================================================
RCS file: /var/cvsroot/gentoo/xml/htdocs/doc/en/gcc-optimization.xml,v
retrieving revision 1.6
retrieving revision 1.7
diff -u -r1.6 -r1.7
--- gcc-optimization.xml	27 Jul 2007 17:34:45 -0000	1.6
+++ gcc-optimization.xml	29 Jul 2007 06:58:08 -0000	1.7
@@ -1,6 +1,6 @@
 <?xml version='1.0' encoding='UTF-8'?>
 
-<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/gcc-optimization.xml,v 1.6 2007/07/27 17:34:45 nightmorph Exp $ -->
+<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/gcc-optimization.xml,v 1.7 2007/07/29 06:58:08 nightmorph Exp $ -->
 
 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
 
@@ -22,8 +22,8 @@
 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
 <license/>
 
-<version>1.3</version>
-<date>2007-07-27</date>
+<version>1.4</version>
+<date>2007-07-28</date>
 
 <chapter>
 <title>Introduction</title>
@@ -271,11 +271,10 @@
   </li>
   <li>
     <c>-O2</c>: A step up from <c>-O1</c>. This is the <e>recommended</e> level
-    of optimization unless you have special needs (such as <c>-Os</c>, as will
-    be explained shortly). <c>-O2</c> will activate a few more flags in addition
-    to the ones activated by <c>-O1</c>. With <c>-O2</c>, the compiler will
-    attempt to increase code performance without compromising on size, and
-    without taking too much compilation time.
+    of optimization unless you have special needs. <c>-O2</c> will activate a
+    few more flags in addition to the ones activated by <c>-O1</c>. With
+    <c>-O2</c>, the compiler will attempt to increase code performance without
+    compromising on size, and without taking too much compilation time.
   </li>
   <li>
     <c>-O3</c>: This is the highest level of optimization possible, and also the
@@ -292,9 +291,11 @@
   </li>
   <li>
     <c>-Os</c>: This level will optimize your code for size. It activates all
-    <c>-O2</c> options that don't increase the size of the generated code. It's
-    useful for machines that have extremely limited disk storage space and/or
-    have CPUs with small cache sizes.
+    <c>-O2</c> options that don't increase the size of the generated code. It
+    can be useful for machines that have extremely limited disk storage space
+    and/or have CPUs with small cache sizes. However, it can cause quite a few
+    problems, which is why it is filtered out by many of the ebuilds in the
+    tree. Using <c>-Os</c> is not recommended.
   </li>
 </ul>
 
@@ -302,8 +303,8 @@
 As previously mentioned, <c>-O2</c> is the recommended optimization level. If
 package compilations error out, check to make sure that you aren't using
 <c>-O3</c>. As a fallback option, try setting your CFLAGS and CXXFLAGS to a
-lower optimization level, such as <c>-O1</c> or <c>-Os</c> and recompile the
-package.
+lower optimization level, such as <c>-O1</c> or even <c>-O0 -g2 -ggdb</c> (for
+error reporting and checking for possible problems) and recompile the package.
 </p>
 
 </body>
@@ -338,10 +339,11 @@
 <p>
 In particular, it makes troubleshooting applications written in Java much
 harder, though Java is not the only code affected by using this flag. So while
-the flag can help, it can also make debugging harder. If you don't plan to do
-much debugging and haven't added any other debugging-related CFLAGS such as
-<c>-ggdb</c> (and you aren't installing packages with the <c>debug</c> USE
-flag), then try using <c>-fomit-frame-pointer</c>.
+the flag can help, it also makes debugging harder; backtraces will be useless.
+However, if you don't plan to do much debugging and haven't added any other
+debugging-related CFLAGS such as <c>-ggdb</c> (and you aren't installing
+packages with the <c>debug</c> USE flag), then try using
+<c>-fomit-frame-pointer</c>.
 </p>
 
 <impo>



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