[wwwdocs] gcc-4.6/porting_to.html
Needs some more work, here's a rough draft.
-benjaminIndex: htdocs/gcc-4.6/porting_to.html
===
RCS file: htdocs/gcc-4.6/porting_to.html
diff -N htdocs/gcc-4.6/porting_to.html
*** /dev/null 1 Jan 1970 00:00:00 -
--- htdocs/gcc-4.6/porting_to.html 17 Mar 2011 06:47:42 -
***
*** 0
--- 1,167
+
+
+
+ GCC 4.6 Release Series — Porting to the New Tools
+
+
+
+ GCC 4.6 Release SeriesPorting to the New Tools
+
+
+ The GCC 4.6 release series differs from previous GCC releases in more
+ than the usual list
+ of http://gcc.gnu.org/gcc-4.6/changes.html";>new
+ features. Some of these changes are a result of bug fixing, and
+ some old behaviors have been intentionally changed in order to support
+ new standards, or relaxed in standards-conforming ways to facilitate
+ compilation or runtime performance. Some of these changes are not
+ visible to the naked eye, and will not cause problems when updating
+ from older GCC versions.
+
+
+
+ However, some of these changes are visible, and can cause grief to
+ users porting to GCC 4.6. This document is an effort to identify major
+ issues and provide clear solutions in a quick and easily-searched
+ manner. Additions and suggestions for improvement are welcome.
+
+
+ C language issues
+
+ New warnings for unused variables and parameters
+
+
+ The behavior of -Wall has changed and now includes the
+ new warning flags -Wunused-but-set-variable and
+ (with -Wall
+ -Wextra) -Wunused-but-set-parameter. This may
+ result in new warnings in code that compiled cleanly with previous
+ versions of GCC.
+
+
+
+ For example,
+
+
+
+ void fn (void)
+ {
+ int foo;
+ foo = bar (); /* foo is never used. */
+ }
+
+
+
+ Gives the following diagnostic:
+
+
+
+ warning: variable âfooâ set but not used [-Wunused-but-set-variable]
+
+
+ Although these warnings will
+ not result in compilation failure, often -Wall is used in
+ conjunction with -Werror and as a result, new warnings
+ are turned into new errors.
+
+
+
+ To fix, first see if the unused variable or parameter can be removed
+ without changing the result or logic of the surrounding code. If not,
+ annoate it with __attribute__((__unused__))
+
+
+ As a workaround, remove -Werror until the new warnings
+ are fixed, or for conversion warnings
+ add -Wno-unused-but-set-variable
+ or -Wno-unused-but-set-parameter.
+
+
+ Strict overflow warnings
+
+
+ Using the -Wstrict-overflow flag
+ with -Werror and optmization flags above -O2
+ may result in compile errors when using glibc optimizations
+ for strcmp.
+
+
+
+ For example,
+
+
+
+ #include
+ void do_rm_rf (const char *p) { if (strcmp (p, "/") == 0) return; }
+
+
+
+ Results in the following diagnostic:
+
+
+
+ error: assuming signed overflow does not occur when changing X +- C1 cmp C2 to X cmp C1 +- C2 [-Werror=strict-overflow]
+
+
+
+ To work around this, use -D__NO_STRING_INLINES.
+
+
+ C++ language issues
+
+ Header dependency changes
+
+
+ Many of the standard C++ library include files have been edited to no
+ longer include to get namespace std
+ -scoped versions of size_t and ptrdiff_t.
+
+
+
+ As such, C++ programs that used the macros NULL
+ or offsetof without including will no
+ longer compile. The diagnostic produced is similar to:
+
+
+
+ error: 'ptrdiff_t' does not name a type
+
+
+
+ error: 'size_t' has not been declared
+
+
+
+ error: 'NULL' was not declared in this scope
+
+
+
+ error: there are no arguments to 'offsetof' that depend on a template
+ parameter, so a declaration of 'offsetof' must be available
+
+
+
+ Fixing this issue is easy, just include .
+
+
+ Java issues
+
+ Links
+
+
+ Jakub Jelinek, http://lists.fedoraproject.org/pipermail/devel/2011-February/148523.html";>GCC 4.6 related common package rebuild failures (was Re: mass rebuild status)
+
+
+
+ Matthias Klose, http://lists.debian.org/debian-devel-announce/2011/02/msg00012.html";>prepare to fix build failures with new GCC versions
+
+
+
+ Jim Meyering, http://lists.fedoraproject.org/pipermail/devel/2011-March/149355.html";>gcc-4.6.0-0.12.fc15.x86_64 breaks strcmp?
+
+
+
+
+
+
+
Re: [wwwdocs] gcc-4.6/porting_to.html
On Wed, 16 Mar 2011, Benjamin Kosnik wrote: > Needs some more work, here's a rough draft. s/Porting to the new tools/Porting to the new version/ ? brgds, H-P
Re: [wwwdocs] gcc-4.6/porting_to.html
On Wed, Mar 16, 2011 at 11:51:30PM -0700, Benjamin Kosnik wrote:
> +
> + To fix, first see if the unused variable or parameter can be removed
> + without changing the result or logic of the surrounding code. If not,
> + annoate it with __attribute__((__unused__))
annotate
Also, I think we should mention that casting the var to void is another
option.
And I think it is worth mentioning that sometimes the RHS can have important
side-effects, in which case it is desirable to just drop the LHS and =,
while sometimes the RHS is just uselessly computed and can be dropped
altogether with the assignment and unused variable.
> + Strict overflow warnings
> +
> +
> + Using the -Wstrict-overflow flag
> + with -Werror and optmization flags above -O2
> + may result in compile errors when using glibc optimizations
> + for strcmp.
> +
> +
> +
> + For example,
> +
> +
> +
> + #include
> + void do_rm_rf (const char *p) { if (strcmp (p, "/") == 0) return; }
> +
This has been actually fixed, so we shouldn't mention this.
> +
> + Jim Meyering, href="http://lists.fedoraproject.org/pipermail/devel/2011-March/149355.html";>gcc-4.6.0-0.12.fc15.x86_64
> breaks strcmp?
And this reference too.
Thanks for writing this.
Jakub
Re: [wwwdocs] gcc-4.6/porting_to.html
On Wed, 16 Mar 2011 23:51:30 -0700 Benjamin Kosnik wrote: > Needs some more work, here's a rough draft. The one I've seen most often other than including cstddef is due to linker options starting with -- (eg. --export-dynamic, --no-undefined) now being errors. Previously they were just silently ignored. The fix of course is to prepend "-Wl," to these flags. http://gcc.gnu.org/PR46410 -- fonts, gcc-porting, it makes no sense how it makes no sense toolchain, wxwidgets but i'll take it free anytime @ gentoo.orgEFFD 380E 047A 4B51 D2BD C64F 8AA8 8346 F9A4 0662 signature.asc Description: PGP signature
Re: [wwwdocs] gcc-4.6/porting_to.html
On 17.03.2011 07:51, Benjamin Kosnik wrote: > > Needs some more work, here's a rough draft. > > -benjamin + As a workaround, remove -Werror until the new warnings + are fixed, or for conversion warnings + add -Wno-unused-but-set-variable + or -Wno-unused-but-set-parameter. + what about recommending keeping -Werror and adding -Wno-error=unused-but-set-variable or -Wno-error=unused-but-set-parameter? Then the warnings remain, but don't cause an error. Matthias
Re: [wwwdocs] gcc-4.6/porting_to.html
Hi Benjamin,
On Wed, 16 Mar 2011, Benjamin Kosnik wrote:
> Needs some more work, here's a rough draft.
I realized this one hasn't made it in, but is really nice. I made a
number of minor edits (typos, markup, simplifying headings,... among
others). What do you think -- should we include this?
Many users still won't have GCC 4.6 deployed yet, so I think it's
still worth it.
What do you think?
Gerald
Index: porting_to.html
===
RCS file: porting_to.html
diff -N porting_to.html
--- /dev/null 1 Jan 1970 00:00:00 -
+++ porting_to.html 11 Oct 2011 04:47:14 -
@@ -0,0 +1,142 @@
+
+
+
+Porting to GCC 4.6
+
+
+
+Porting to GCC 4.6
+
+
+The GCC 4.6 release series differs from previous GCC releases in more
+than the usual list of
+http://gcc.gnu.org/gcc-4.6/changes.html";>changes. Some of
+these are a result of bug fixing, and some old behaviors have been
+intentionally changed in order to support new standards, or relaxed
+instandards-conforming ways to facilitate compilation or runtime
+performance. Some of these changes are not visible to the naked eye
+and will not cause problems when updating from older versions.
+
+
+
+However, some of these changes are visible, and can cause grief to
+users porting to GCC 4.6. This document is an effort to identify major
+issues and provide clear solutions in a quick and easily searched
+manner. Additions and suggestions for improvement are welcome.
+
+
+C language issues
+
+New warnings for unused variables and parameters
+
+
+The behavior of -Wall has changed and now includes the
+new warning flags -Wunused-but-set-variable and
+(with -Wall
+-Wextra) -Wunused-but-set-parameter. This may
+result in new warnings in code that compiled cleanly with previous
+versions of GCC.
+
+
+
+For example,
+
+ void fn (void)
+ {
+int foo;
+foo = bar (); /* foo is never used. */
+ }
+
+Gives the following diagnostic:
+
+warning: variable "foo" set but not used [-Wunused-but-set-variable]
+
+
+low flag
+with -Werror and optimization flags above -O2
+may result in compile errors when using glibc optimizations
+for strcmp.
+
+
+
+For example,
+
+#include
+void do_rm_rf (const char *p) { if (strcmp (p, "/") == 0) return; }
+
+Results in the following diagnostic:
+
+error: assuming signed overflow does not occur when changing X +- C1 cmp C2 to
X cmp C1 +- C2 [-Werror=strict-overflow]
+
+
+
+
+To work around this, use -D__NO_STRING_INLINES.
+
+
+C++ language issues
+
+Header dependency changes
+
+
+Many of the standard C++ library include files have been edited to no
+longer include to get namespace std
+-scoped versions of size_t and ptrdiff_t.
+
+
+
+As such, C++ programs that used the macros NULL
+or offsetof without including will no
+longer compile. The diagnostic produced is similar to:
+
+
+
+error: 'ptrdiff_t' does not name a type
+
+
+
+error: 'size_t' has not been declared
+
+
+
+error: 'NULL' was not declared in this scope
+
+
+
+error: there are no arguments to 'offsetof' that depend on a template
+parameter, so a declaration of 'offsetof' must be available
+
+
+
+Fixing this issue is easy: just include .
+
+
+
+
+Links
+
+
+Jakub Jelinek,
+ http://lists.fedoraproject.org/pipermail/devel/2011-February/148523.html";>GCC
+4.6 related common package rebuild failures (was Re: mass rebuild status)
+
+
+
+Matthias Klose,
+http://lists.debian.org/debian-devel-announce/2011/02/msg00012.html";>prepare
+to fix build failures with new GCC versions
+
+
+
+Jim Meyering,
+ http://lists.fedoraproject.org/pipermail/devel/2011-March/149355.html";>gcc-4.6.0-0.12.fc15.x86_64
breaks strcmp?
+
+
+
+
+
+
+
+
Re: [wwwdocs] gcc-4.6/porting_to.html
> I realized this one hasn't made it in, but is really nice. I made a > number of minor edits (typos, markup, simplifying headings,... among > others). What do you think -- should we include this? > > Many users still won't have GCC 4.6 deployed yet, so I think it's > still worth it. > > What do you think? Ouch. I see this is not in, and I though I checked in the draft months ago. Please check this in immediately!!! -benjamin
Re: [wwwdocs] gcc-4.6/porting_to.html
On Tue, 11 Oct 2011, Benjamin Kosnik wrote:
>> Many users still won't have GCC 4.6 deployed yet, so I think it's
>> still worth it.
> Ouch. I see this is not in, and I though I checked in the draft months
> ago.
>
> Please check this in immediately!!!
Done last evening, and made some further tweaks.
For reference hre is the full patch that's now live on the system.
Gerald
Index: porting_to.html
===
RCS file: porting_to.html
diff -N porting_to.html
--- /dev/null 1 Jan 1970 00:00:00 -
+++ porting_to.html 12 Oct 2011 16:16:54 - 1.3
@@ -0,0 +1,150 @@
+
+
+
+Porting to GCC 4.6
+
+
+
+Porting to GCC 4.6
+
+
+The GCC 4.6 release series differs from previous GCC releases in more
+than the usual list of
+http://gcc.gnu.org/gcc-4.6/changes.html";>changes. Some of
+these are a result of bug fixing, and some old behaviors have been
+intentionally changed in order to support new standards, or relaxed
+instandards-conforming ways to facilitate compilation or runtime
+performance. Some of these changes are not visible to the naked eye
+and will not cause problems when updating from older versions.
+
+
+
+However, some of these changes are visible, and can cause grief to
+users porting to GCC 4.6. This document is an effort to identify major
+issues and provide clear solutions in a quick and easily searched
+manner. Additions and suggestions for improvement are welcome.
+
+
+C language issues
+
+New warnings for unused variables and parameters
+
+
+The behavior of -Wall has changed and now includes the
+new warning flags -Wunused-but-set-variable and
+(with -Wall
+-Wextra) -Wunused-but-set-parameter. This may
+result in new warnings in code that compiled cleanly with previous
+versions of GCC.
+
+
+For example,
+
+ void fn (void)
+ {
+int foo;
+foo = bar (); /* foo is never used. */
+ }
+
+Gives the following diagnostic:
+
+warning: variable "foo" set but not used [-Wunused-but-set-variable]
+
+
+Although these warnings will not result in compilation failure,
+often -Wall is used in conjunction with
+-Werror and as a result, new warnings are turned into
+new errors.
+
+To fix, first see if the unused variable or parameter can be removed
+without changing the result or logic of the surrounding code. If not,
+annotate it with __attribute__((__unused__)).
+
+As a workaround, remove -Werror until the new warnings
+are fixed. For conversion warnings add
+-Wno-unused-but-set-variable or
+-Wno-unused-but-set-parameter.
+
+Strict overflow warnings
+
+Using the -Wstrict-overflow flag with
+-Werror and optmization flags above -O2
+may result in compile errors when using glibc optimizations
+for strcmp.
+
+For example,
+
+#include
+void do_rm_rf (const char *p) { if (strcmp (p, "/") == 0) return; }
+
+Results in the following diagnostic:
+
+error: assuming signed overflow does not occur when changing X +- C1 cmp C2 to
X cmp C1 +- C2 [-Werror=strict-overflow]
+
+
+To work around this, use -D__NO_STRING_INLINES.
+
+C++ language issues
+
+Header dependency changes
+
+
+Many of the standard C++ library include files have been edited to no
+longer include to get namespace std
+-scoped versions of size_t and ptrdiff_t.
+
+
+
+As such, C++ programs that used the macros NULL
+or offsetof without including will no
+longer compile. The diagnostic produced is similar to:
+
+
+
+error: 'ptrdiff_t' does not name a type
+
+
+
+error: 'size_t' has not been declared
+
+
+
+error: 'NULL' was not declared in this scope
+
+
+
+error: there are no arguments to 'offsetof' that depend on a template
+parameter, so a declaration of 'offsetof' must be available
+
+
+
+Fixing this issue is easy: just include .
+
+
+
+
+Links
+
+
+Jakub Jelinek,
+ http://lists.fedoraproject.org/pipermail/devel/2011-February/148523.html";>GCC
+4.6 related common package rebuild failures (was Re: mass rebuild status)
+
+
+
+Matthias Klose,
+http://lists.debian.org/debian-devel-announce/2011/02/msg00012.html";>prepare
+to fix build failures with new GCC versions
+
+
+
+Jim Meyering,
+ http://lists.fedoraproject.org/pipermail/devel/2011-March/149355.html";>gcc-4.6.0-0.12.fc15.x86_64
breaks strcmp?
+
+
+
+
+
+
Re: [wwwdocs] gcc-4.6/porting_to.html
On Mon, 10 Oct 2011, Gerald Pfeifer wrote: > I realized this one hasn't made it in, but is really nice. I made a > number of minor edits (typos, markup, simplifying headings,... among > others). What do you think -- should we include this? Checking mailing list archives I realized that Jakub had provided feedback ( http://gcc.gnu.org/ml/gcc-patches/2011-03/msg00987.html ) that the strict overflow warnings had been fixed. Hence I went ahead and committed the removal below. Gerald Index: porting_to.html === RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.6/porting_to.html,v retrieving revision 1.3 diff -u -r1.3 porting_to.html --- porting_to.html 12 Oct 2011 16:16:54 - 1.3 +++ porting_to.html 24 Oct 2011 00:52:53 - @@ -65,24 +65,6 @@ -Wno-unused-but-set-variable or -Wno-unused-but-set-parameter. -Strict overflow warnings - -Using the -Wstrict-overflow flag with --Werror and optmization flags above -O2 -may result in compile errors when using glibc optimizations -for strcmp. - -For example, - -#include-void do_rm_rf (const char *p) { if (strcmp (p, "/") == 0) return; } - -Results in the following diagnostic: - -error: assuming signed overflow does not occur when changing X +- C1 cmp C2 to X cmp C1 +- C2 [-Werror=strict-overflow] - - -To work around this, use -D__NO_STRING_INLINES. C++ language issues @@ -139,11 +121,6 @@ to fix build failures with new GCC versions - -Jim Meyering, - http://lists.fedoraproject.org/pipermail/devel/2011-March/149355.html";>gcc-4.6.0-0.12.fc15.x86_64 breaks strcmp? - -
Re: [wwwdocs] gcc-4.6/porting_to.html
[Sorry for the delay, catching up after being away] Gerald Pfeifer writes: > On Mon, 10 Oct 2011, Gerald Pfeifer wrote: >> I realized this one hasn't made it in, but is really nice. I made a >> number of minor edits (typos, markup, simplifying headings,... among >> others). What do you think -- should we include this? > > Checking mailing list archives I realized that Jakub had provided > feedback ( http://gcc.gnu.org/ml/gcc-patches/2011-03/msg00987.html ) > that the strict overflow warnings had been fixed. > > Hence I went ahead and committed the removal below. Thanks for doing this. I noticed a typo while reading it, so I committed the patch below as obvious. Richard Index: porting_to.html === RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.6/porting_to.html,v retrieving revision 1.4 diff -u -r1.4 porting_to.html --- porting_to.html 24 Oct 2011 00:57:54 - 1.4 +++ porting_to.html 15 Nov 2011 13:38:10 - @@ -13,7 +13,7 @@ http://gcc.gnu.org/gcc-4.6/changes.html";>changes. Some of these are a result of bug fixing, and some old behaviors have been intentionally changed in order to support new standards, or relaxed -instandards-conforming ways to facilitate compilation or runtime +in standards-conforming ways to facilitate compilation or runtime performance. Some of these changes are not visible to the naked eye and will not cause problems when updating from older versions.
Re: [wwwdocs] gcc-4.6/porting_to.html
On Wed, 12 Oct 2011, Gerald Pfeifer wrote: > For reference hre is the full patch that's now live on the system. And this take into account a suggestion by Matthias Klose (cf. http://gcc.gnu.org/ml/gcc-patches/2011-03/msg01014.html ). Applied. Gerald Index: porting_to.html === RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.6/porting_to.html,v retrieving revision 1.5 diff -u -r1.5 porting_to.html --- porting_to.html 15 Nov 2011 13:38:24 - 1.5 +++ porting_to.html 19 Nov 2011 16:56:39 - @@ -60,10 +60,9 @@ without changing the result or logic of the surrounding code. If not, annotate it with __attribute__((__unused__)). -As a workaround, remove -Werror until the new warnings -are fixed. For conversion warnings add --Wno-unused-but-set-variable or --Wno-unused-but-set-parameter. +As a workaround, add +-Wno-error=unused-but-set-variable or +-Wno-error=unused-but-set-parameter. C++ language issues
[wwwdocs] gcc-4.6/porting_to.html -- lists.fedoraproject.org is on https now
This is the only reference to lists.fedoraproject.org that I found via http; all others already are https. Committed. Index: gcc-4.6/porting_to.html === RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.6/porting_to.html,v retrieving revision 1.8 diff -u -r1.8 porting_to.html --- gcc-4.6/porting_to.html 28 Jun 2015 14:54:03 - 1.8 +++ gcc-4.6/porting_to.html 28 Feb 2016 19:42:35 - @@ -109,7 +109,7 @@ Jakub Jelinek, - http://lists.fedoraproject.org/pipermail/devel/2011-February/148523.html";>GCC + https://lists.fedoraproject.org/pipermail/devel/2011-February/148523.html";>GCC 4.6 related common package rebuild failures (was Re: mass rebuild status)
