[Bug libfortran/36857] Non-English locale breaks gfortran float formatting ("printf is broken")

["kargl at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #5 from kargl at gcc dot gnu dot org  2008-07-19 20:23 -------
(In reply to comment #4)
> Does setting the locale to POSIX in the above patch fix the issue if the
> program using the runtime for example changes the locale just before calling a
> Fortran routine that does some printing?

The patch sets locale to POSIX for both the gfortran frontend and the
runtime library.  POSIX defines the LC_NUMERIC decimal glyph to be
a period.

> Also, does the locale change affect other parts of the program calling the
> gfortran runtime?

If the other parts are written in Fortran, then no affect.  In a mixed
language environment see below.

> If the program is threaded? If yes, just changing the locale
> may cause some unexpected problems for the caller.

Should have no effect on threaded apps. 

> 
> The reason I noticed this bug was that a user of the Scipy library (a
> scientific library, for Python, that includes some routines written in Fortran)
> was experiencing a mysterious "printf is broken" error when writing a program
> using the library. In this case at least, locale was probably changed after
> libgfortran was loaded, and it would be unexpected if calling a Fortran routine
> changed the locale.
> 

The Fortran standard is silent with respect to locale.  The patch I propose
has gfortran enforce POSIX locale.  It is the programmers responsibility to
handle it in a mixed language environment.  The pseudocode is

   getlocale()              /* Get current locale */
   call_gfortran_routine()  /* gfc enforces POSIX */
   setlocale()              /* Restore the locale from getlocale */



Of course, this is IMHO.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36857