X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=functions%2Fstdio%2Fftell.c;h=f4bd300713c60b92b9f4a06f223c4ed24719c23b;hb=d865c4403fc91d1f1ac95ba76febcee9f429bb97;hp=e392a8b1f01de37121a2683c6a8ab2643f4d326d;hpb=f495ef679088649341da616b815ddc7ff60cec7b;p=pdclib

diff --git a/functions/stdio/ftell.c b/functions/stdio/ftell.c
index e392a8b..f4bd300 100644
--- a/functions/stdio/ftell.c
+++ b/functions/stdio/ftell.c
@@ -1,5 +1,3 @@
-/* $Id$ */
-
 /* ftell( FILE * )
 
    This file is part of the Public Domain C Library (PDCLib).
@@ -28,12 +26,11 @@ long int ftell( struct _PDCLIB_file_t * stream )
            i.e. unprocessed bytes as positive number.
        That is how the somewhat obscure return-value calculation works.
     */
-    /* If offset is too large for return type, report error instead of wrong
-       offset value. Buffers may not be larger than INT_MAX so the casts are
-       safe.
+    /*  If offset is too large for return type, report error instead of wrong
+        offset value.
     */
-    /* FIXME: This calculation *underflows* when offset smaller than pre-read */
-    if ( ( stream->pos.offset - ( (int)stream->bufend + (int)stream->ungetidx ) ) > ( LONG_MAX - stream->bufidx ) )
+    /* TODO: Check what happens when ungetc() is called on a stream at offset 0 */
+    if ( ( stream->pos.offset - stream->bufend ) > ( LONG_MAX - ( stream->bufidx - stream->ungetidx ) ) )
     {
         /* integer overflow */
         _PDCLIB_errno = _PDCLIB_ERANGE;
@@ -45,7 +42,8 @@ long int ftell( struct _PDCLIB_file_t * stream )
 #endif
 
 #ifdef TEST
-#include <_PDCLIB_test.h>
+
+#include "_PDCLIB_test.h"
 
 #include <stdlib.h>
 
@@ -63,6 +61,13 @@ int main( void )
     FILE * fh;
     TESTCASE( ( fh = tmpfile() ) != NULL );
     TESTCASE( setvbuf( fh, buffer, _IOLBF, 4 ) == 0 );
+    /* Testing ungetc() at offset 0 */
+    rewind( fh );
+    TESTCASE( ungetc( 'x', fh ) == 'x' );
+    TESTCASE( ftell( fh ) == -1l );
+    rewind( fh );
+    TESTCASE( ftell( fh ) == 0l );
+    /* Commence "normal" tests */
     TESTCASE( fputc( '1', fh ) == '1' );
     TESTCASE( fputc( '2', fh ) == '2' );
     TESTCASE( fputc( '3', fh ) == '3' );
@@ -93,4 +98,3 @@ int main( void )
 }
 
 #endif
-