bugGNU gettext - Bugs: bug #64006, *printf() defines break C++ builds...

 
 

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bug #64006: *printf() defines break C++ builds (specifically Qt)

Submitter:  Pierre Ossman <cendossm>
Submitted:  Thu 06 Apr 2023 08:52:37 AM UTC
   
 
Category:  Programmer interface Severity:  3 - Normal
Item Group:  None Status:  Confirmed
Privacy:  Public Assigned to:  None
Open/Closed:  Open

Jump to the original submission

Tue 13 Jun 2023 12:16:33 PM UTC, comment #9: 

For c++11 and later, variadic templates can be used:


#if __cplusplus >= 201103L
template<typename ... Args>
void asprintf(const char* x, Args ... args)
{
    libintl_asprintf(x, args ... );
}
#else
%define asprintf libintl_asprintf
#endif


Stefan BrĂ¼ns <stefanbruens>
Fri 02 Jun 2023 08:13:52 AM UTC, comment #8: 

Oh, I completely misunderstood then. I thought it was both or neither. Thank you for that clarification!

Pierre Ossman <cendossm>
Fri 02 Jun 2023 08:06:20 AM UTC, comment #7: 


> it would be very helpful for our programmers to make sure that they actually use the position markers where things need to be translated.


The programmer does not need to use the position markers. The programmer can use just "bla %s blabla %s", and it's the translator who introduces the position markers when reordering.

Bruno Haible <haible>
Group administrator
Fri 02 Jun 2023 07:40:53 AM UTC, comment #6: 

Oh, I just realised that once we fix up this support, it would be very helpful for our programmers to make sure that they actually use the position markers where things need to be translated.

Are there any tools that can assist with enforcing that?

(sorry for the comment spam)

Pierre Ossman <cendossm>
Fri 02 Jun 2023 07:39:28 AM UTC, comment #5: 

Great. That at least slightly reduced the issue from a current bug that needs to be urgently addressed, to an eventually required feature.

Thank you for the insight!

Pierre Ossman <cendossm>
Fri 02 Jun 2023 12:09:54 AM UTC, comment #4: 


> if neither the programmer nor the translator use the position markers, will gettext implicitly add them in any scenario?


No, gettext will not add %1$ or such. It returns what the translator has provided in the PO file, assuming it has been checked through "msgfmt -c".

There is no tool that tests whether a translator has used this syntax, and frankly we don't want to have such a tool. It would be bad to tell the translators "you cannot reorder arguments, as required for your language, because one of the target platforms of the application is Windows and the programmer has not been able rectify this platform's printf deficiencies."

Bruno Haible <haible>
Group administrator
Thu 01 Jun 2023 02:57:45 PM UTC, comment #3: 


comment #2:

> The reason is that translators need the freedom to reorder arguments within format strings, see https://www.gnu.org/software/gettext/manual/html_node/c_002dformat-Flag.html
>
> If a system's printf implementation does not support this, the output will be non-intelligible to users.
>


Yes, that is a big problem. But if neither the programmer nor the translator use the position markers, will gettext implicitly add them in any scenario?

Pierre Ossman <cendossm>
Thu 01 Jun 2023 01:43:57 PM UTC, comment #2: 


> I'm wondering why there *printf() replacements are unconditionally included, with no way to turn them off?


They are included on platforms that need them, in particular on native Windows.

The reason is that translators need the freedom to reorder arguments within format strings, see https://www.gnu.org/software/gettext/manual/html_node/c_002dformat-Flag.html

If a system's printf implementation does not support this, the output will be non-intelligible to users.

> we have convenience functions that take format strings in many places


You have to look whether the format string interpreter actually supports the %1$, %2$, etc. syntax.

Bruno Haible <haible>
Group administrator
Thu 06 Apr 2023 08:56:36 AM UTC, comment #1: 

I'm wondering why there *printf() replacements are unconditionally included, with no way to turn them off?

Does gettext have assumptions that require the POSIX behaviour? Or did you figure that everyone needs the argument position feature to make life easier for the translators?

If it's the former, then we probably break that assumption in many places, as we have convenience functions that take format strings in many places. :/

Pierre Ossman <cendossm>
Thu 06 Apr 2023 08:52:37 AM UTC, original submission:  

gettext tries to redirect the various *printf() functions to its own implementation if the platform version doesn't comply to the POSIX behaviour.

Unfortunately, it does this using #define:s, which isn't very compatible with C++ and the namespacing there. It is more careful about C++ when handling the various *gettext() functions, but not here.

A specific scenario where this breaks is when using Qt's QString::asprintf():

D:/a/tigervnc/tigervnc/vncviewer/vncconnection.cxx:1727:24: error: 'libintl_asprintf' is not a member of 'QString'
 1727 |   infoText += QString::asprintf(_("Security method: %s\n"), rfb::secTypeName(m_securityType));
      |                        ^~~~~~~~
make[2]: * [vncviewer/CMakeFiles/vncviewer.dir/build.make:255: vncviewer/CMakeFiles/vncviewer.dir/vncconnection.cxx.obj] Error 1

More complete build log here:

https://github.com/CendioOssman/tigervnc/actions/runs/4626832263/jobs/8184028650

Pierre Ossman <cendossm>

 

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    Follows 1 latest change.

    Date Changed by Updated Field Previous Value => Replaced by
    2023-04-06 haible StatusNone Confirmed

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