Go back to my original idea of checking for EILSEQ and EINVAL and failing

immediately if either of those is set after wxVsnprintf call returns a
negative number to indicate some type of failure.

All other errno are assumed to simply mean that the buffer is undersized so
the platform C library function can set errno to anything it likes or simply
not set it at all and our code will keep trying to increase the buffer size
just as it did originally.

This should (hopefully) fix compilation with C libraries that only support
the most basic set of errors (of which EINVAL and EILSEQ are part).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@49342 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/src/common/string.cpp b/src/common/string.cpp
index 84f285410c0efcf1fbfc7ebbedbe7dfa364c5fb7..5db2ba07a60fb909748ff456fdf5e6b1f6fd3ae6 100644 (file)
--- a/src/common/string.cpp
+++ b/src/common/string.cpp
@@ -1603,12 +1603,24 @@ int wxString::DoPrintfUtf8(const char *format, ...)
     and set errno.
 
     What vswprintf sets errno to is undefined but Darwin seems to set it to
-    EOVERFLOW.  The only expected errno that are defined anywhere are by an
-    addendum indicating that EILSEQ should be set for bad input characters and
-    EINVALID for bad arguments such as a NULL buffer pointer.  It would appear
-    that setting EOVERFLOW is not documented anywhere and has only been at
-    this time observed on Darwin.
-
+    EOVERFLOW.  The only expected errno are EILSEQ and EINVAL.  Both of
+    those are defined in the standard and backed up by several conformance
+    statements.  Note that ENOMEM mentioned in the manual page does not
+    apply to swprintf, only wprintf and fwprintf.
+
+    Official manual page:
+    http://www.opengroup.org/onlinepubs/009695399/functions/swprintf.html
+
+    Some conformance statements (AIX, Solaris):
+    http://www.opengroup.org/csq/view.mhtml?RID=ibm%2FSD1%2F3
+    http://www.theopengroup.org/csq/view.mhtml?norationale=1&noreferences=1&RID=Fujitsu%2FSE2%2F10
+
+    Since EILSEQ and EINVAL are rather common but EOVERFLOW is not and since
+    EILSEQ and EINVAL are specifically defined to mean the error is other than
+    an undersized buffer and no other errno are defined we treat those two
+    as meaning hard errors and everything else gets the old behavior which
+    is to keep looping and increasing buffer size until the function succeeds.
+ 
     In practice it's impossible to determine before compilation which behavior
     may be used.  The vswprintf function may have vsnprintf-like behavior or
     vice-versa.  Behavior detected on one release can theoretically change
@@ -1704,16 +1716,15 @@ static int DoStringPrintfV(wxString& str,
             // as we don't know how much we need, double the current size of
             // the buffer
 #ifndef __WXWINCE__
-            if( (errno == 0) || (errno == EOVERFLOW) )
+            if( (errno == EILSEQ) || (errno == EINVAL) )
+            // If errno was set to one of the two well-known hard errors
+            // then fail immediately to avoid an infinite loop.
+                return -1;
+            else
+#endif // __WXWINCE__
             // still not enough, as we don't know how much we need, double the
             // current size of the buffer
                 size *= 2;
-            else
-            // If errno was set to something else, assume hard failure.
-                return -1;
-#else
-            size *= 2;
-#endif // __WXWINCE__
 #endif // wxUSE_WXVSNPRINTF/!wxUSE_WXVSNPRINTF
         }
         else if ( len >= size )