bugfix: sf.net #899 trim( wstring ) causes crash if string is single space

- avoid returning a pointer before the first element in fb_wstr_SkipCharRev(), &s[-1] is undefined behaviour
- also then avoids passing start > end pointers to fb_wstr_CalcDiff()
- fb_wstr_SkipCharRev() now returns a pointer to the start of all skipped chars, or the end marker if no chars are skipped

Author: jayrm

src/rtlib/fb_unicode.h

@@ -220,12 +220,12 @@ static __inline__ const FB_WCHAR *fb_wstr_SkipCharRev( const FB_WCHAR *s, ssize_
 		return s;
 
 	/* fixed-len's are filled with null's as in PB, strip them too */
-	const FB_WCHAR *p = &s[chars-1];
+	const FB_WCHAR *p = &s[chars];
 	while( chars > 0 )
 	{
-		if( *p != c )
-			return p;
 		--p;
+		if( *p != c )
+			return ++p;
 		--chars;
 	}
 

src/rtlib/strw_ltrimex.c

@@ -20,7 +20,7 @@ FBCALL FB_WCHAR *fb_WstrLTrimEx ( const FB_WCHAR *src, const FB_WCHAR *pattern )
                 p = fb_wstr_SkipChar( src,
                                       len,
                                       *pattern );
-                len = len - (ssize_t)(p - src);
+                len -= fb_wstr_CalcDiff( src, p );
 
             } else if( len_pattern != 0 ) {
                 p = src;

src/rtlib/strw_rtrim.c

@@ -16,7 +16,7 @@ FBCALL FB_WCHAR *fb_WstrRTrim ( const FB_WCHAR *src )
 		return NULL;
 
 	p = fb_wstr_SkipCharRev( src, chars, _LC(' ') );
-	chars = fb_wstr_CalcDiff( src, p ) + 1;
+	chars = fb_wstr_CalcDiff( src, p );
 	if( chars <= 0 )
 		return NULL;
 

src/rtlib/strw_rtrimex.c

@@ -21,7 +21,7 @@ FBCALL FB_WCHAR *fb_WstrRTrimEx ( const FB_WCHAR *src, const FB_WCHAR *pattern )
                 p = fb_wstr_SkipCharRev( src,
                                          len,
                                          *pattern );
-                len = (ssize_t)(p - src) + 1;
+                len = fb_wstr_CalcDiff( src, p );
 
             } else if( len_pattern != 0 ) {
                 ssize_t test_index = len - len_pattern;

src/rtlib/strw_trim.c

@@ -16,7 +16,7 @@ FBCALL FB_WCHAR *fb_WstrTrim ( const FB_WCHAR *src )
 		return NULL;
 
 	p = fb_wstr_SkipCharRev( src, chars, _LC(' ') );
-	chars = fb_wstr_CalcDiff( src, p ) + 1;
+	chars = fb_wstr_CalcDiff( src, p );
 	if( chars <= 0 )
 		return NULL;
 
@@ -26,7 +26,7 @@ FBCALL FB_WCHAR *fb_WstrTrim ( const FB_WCHAR *src )
 		return NULL;
 
 	/* alloc temp string */
-    dst = fb_wstr_AllocTemp( chars );
+	dst = fb_wstr_AllocTemp( chars );
 	if( dst != NULL )
 	{
 		/* simple copy */

src/rtlib/strw_trimex.c

@@ -20,7 +20,7 @@ FBCALL FB_WCHAR *fb_WstrTrimEx ( const FB_WCHAR *src, const FB_WCHAR *pattern )
                 p = fb_wstr_SkipChar( src,
                                       len,
                                       *pattern );
-                len = len - (ssize_t)(p - src);
+                len -= fb_wstr_CalcDiff( src, p );
 
             } else if( len_pattern != 0 ) {
                 p = src;
@@ -38,7 +38,7 @@ FBCALL FB_WCHAR *fb_WstrTrimEx ( const FB_WCHAR *src, const FB_WCHAR *pattern )
                     fb_wstr_SkipCharRev( p,
                                          len,
                                          *pattern );
-                len = (ssize_t)(p_tmp - p) + 1;
+                len = fb_wstr_CalcDiff( p, p_tmp );
 
             } else if( len_pattern != 0 ) {
                 ssize_t test_index = len - len_pattern;