[Bug tree-optimization/82700] ICE in printf-return-value with -fexec-charset=EBCDIC-US: converting to execution character set: Invalid or incomplete multibyte or wide character

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82700

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The ICE is caused by the EBCDIC-US character set in Fedora 25 apparently not
including the equivalent of the backslash character.  That makes the charset
invalid, since C requires both the basic source and basic character sets to
include it.  From the comment in the file:

  /* The subset of the source character set used by printf conversion
     specifications (strictly speaking, not all letters are used but
     they are included here for the sake of simplicity).  The dollar
     sign must be included even though it's not in the basic source
     character set.  */
  const char srcset[] = " 0123456789!\"#%&'()*+,-./:;<=>?[\\]^_{|}~$"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

The sprintf pass calls lang_hooks.to_target_charset () to convert each of these
characters from the source set to the execution set and the function aborts
when it can't do the conversion.  That seems unfriendly -- it should instead
return some failure code and let the caller decide how to deal with it.