diff mbox series

GCC-13/changes: Add note about iostream usage

Message ID 20230426165347.599616-1-apinski@marvell.com
State Unresolved
Headers
Series GCC-13/changes: Add note about iostream usage |

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Context Check Description
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Commit Message

Andrew Pinski April 26, 2023, 4:53 p.m. UTC 
  This adds a note about iostream usage so it does not catch others
in surpise like it has already.

OK?
---
 htdocs/gcc-13/changes.html | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Jonathan Wakely April 26, 2023, 7:06 p.m. UTC | #1 
On 26/04/23 09:53 -0700, Andrew Pinski wrote:
>This adds a note about iostream usage so it does not catch others
>in surpise like it has already.
>
>OK?

Thanks, I agree we should add something, but have some comments below.

>---
> htdocs/gcc-13/changes.html | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/htdocs/gcc-13/changes.html b/htdocs/gcc-13/changes.html
>index 70732ec0..7c83f7c4 100644
>--- a/htdocs/gcc-13/changes.html
>+++ b/htdocs/gcc-13/changes.html
>@@ -25,6 +25,11 @@ You may also want to check out our
> <!-- .................................................................. -->
> <h2>Caveats</h2>
> <ul>
>+    <li>libstdc++ uses constructors inside the library to initialize std::cout/std::cin, etc.
>+     instead of having it done in each source which uses iostream header.

We should use code font for std::cout, std::cin and iostream, and
style it as <iostream> not just iostream.

>+     This requires you to make sure the dynamic loader to load the new libstdc++v3 library
>+     (examples of how to do this is to use -Wl,-rpath,... while linking or LD_LIBRARY_PATH
>+     while running the program).  </li>

I think it would be better to link to 
https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dynamic_or_shared.html#manual.intro.using.linkage.dynamic

How about:

   <li>For C++, construction of the global iostream objects 
   <code>std::cout</code>, <code>std::cin</code> etc. is now done
   inside the standard library, instead of in every source file that
   includes the <code>&lt;iostream&gt;</code> header. This change
   improves the start-up performance of C++ programs, but it means that
   code compiled with GCC 13.1 will crash if the correct version of
   <code>libstdc++.so</code> is not used at runtime. See the
   <a href="https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dynamic_or_shared.html#manual.intro.using.linkage.dynamic">documentation</a>
   about using the right <code>libstdc++.so</code> at runtime.
   </li>
Andrew Pinski April 26, 2023, 7:10 p.m. UTC | #2 
On Wed, Apr 26, 2023 at 12:07 PM Jonathan Wakely via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On 26/04/23 09:53 -0700, Andrew Pinski wrote:
> >This adds a note about iostream usage so it does not catch others
> >in surpise like it has already.
> >
> >OK?
>
> Thanks, I agree we should add something, but have some comments below.
>
> >---
> > htdocs/gcc-13/changes.html | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> >diff --git a/htdocs/gcc-13/changes.html b/htdocs/gcc-13/changes.html
> >index 70732ec0..7c83f7c4 100644
> >--- a/htdocs/gcc-13/changes.html
> >+++ b/htdocs/gcc-13/changes.html
> >@@ -25,6 +25,11 @@ You may also want to check out our
> > <!-- .................................................................. -->
> > <h2>Caveats</h2>
> > <ul>
> >+    <li>libstdc++ uses constructors inside the library to initialize std::cout/std::cin, etc.
> >+     instead of having it done in each source which uses iostream header.
>
> We should use code font for std::cout, std::cin and iostream, and
> style it as <iostream> not just iostream.
>
> >+     This requires you to make sure the dynamic loader to load the new libstdc++v3 library
> >+     (examples of how to do this is to use -Wl,-rpath,... while linking or LD_LIBRARY_PATH
> >+     while running the program).  </li>
>
> I think it would be better to link to
> https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dynamic_or_shared.html#manual.intro.using.linkage.dynamic
>
> How about:
>
>    <li>For C++, construction of the global iostream objects
>    <code>std::cout</code>, <code>std::cin</code> etc. is now done
>    inside the standard library, instead of in every source file that
>    includes the <code>&lt;iostream&gt;</code> header. This change
>    improves the start-up performance of C++ programs, but it means that
>    code compiled with GCC 13.1 will crash if the correct version of
>    <code>libstdc++.so</code> is not used at runtime. See the
>    <a href="https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dynamic_or_shared.html#manual.intro.using.linkage.dynamic">documentation</a>
>    about using the right <code>libstdc++.so</code> at runtime.
>    </li>

This looks better than my version.

Thanks,
Andrew

>
>
diff mbox series

Patch

diff --git a/htdocs/gcc-13/changes.html b/htdocs/gcc-13/changes.html
index 70732ec0..7c83f7c4 100644
--- a/htdocs/gcc-13/changes.html
+++ b/htdocs/gcc-13/changes.html
@@ -25,6 +25,11 @@  You may also want to check out our
 <!-- .................................................................. -->
 <h2>Caveats</h2>
 <ul>
+    <li>libstdc++ uses constructors inside the library to initialize std::cout/std::cin, etc.
+     instead of having it done in each source which uses iostream header.
+     This requires you to make sure the dynamic loader to load the new libstdc++v3 library
+     (examples of how to do this is to use -Wl,-rpath,... while linking or LD_LIBRARY_PATH
+     while running the program).  </li>
     <li>OpenMP offloading to Intel MIC has been removed.</li>
     <li>The support for the <code>cr16-elf</code>, <code>tilegx*-linux</code>, <code>tilepro*-linux</code>,
       <code>hppa[12]*-*-hpux10*</code>, <code>hppa[12]*-*-hpux11*</code>