[PATCH] xemit.c: fix a [-Wchar-subscripts] compiler warning

Ramsay Jones· May 25, 2016, 23:06 UTC · lore

While compiling on cygwin (x86_64), gcc complains thus:

      CC xdiff/xemit.o
  xdiff/xemit.c: In function ‘is_empty_rec’:
  xdiff/xemit.c:163:2: warning: array subscript has type ‘char’ [-Wchar-subscripts]
    while (len > 0 && isspace(*rec)) {
    ^

A comment in the <ctype.h> header reads, in part, like so:

   These macros are intentionally written in a manner that will trigger
   a gcc -Wall warning if the user mistakenly passes a 'char' instead
   of an int containing an 'unsigned char'.

In order to suppress the warning, cast the 'char *' pointer 'rec' to an 'unsigned char *' pointer, prior to passing the dereferenced pointer to the isspace() macro.

Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
---

Hi René,

If you need to re-roll your 'rs/xdiff-hunk-with-func-line' branch, could you please squash this (or something like it) into the relevant patch.

[A comment in the linux <ctype.h> header, says that the ctype-info tables ...
   point into arrays of 384, so they can be indexed by any `unsigned
   char' value [0,255]; by EOF (-1); or by any `signed char' value
   [-128,-1).
So, this is not a problem on linux.]

Thanks!

ATB, Ramsay Jones

 xdiff/xemit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Show changes to xdiff/xemit.c +1 −1

diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index d0c0738..ae9adac 100644
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -160,7 +160,7 @@ static int is_empty_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri)
 	const char *rec;
 	long len = xdl_get_rec(xdf, ri, &rec);
 
-	while (len > 0 && isspace(*rec)) {
+	while (len > 0 && isspace(*((unsigned char *)rec))) {
 		rec++;
 		len--;
 	}

-- 
2.8.0

René Scharfe· May 26, 2016, 02:22 UTC · re: Ramsay Jones · lore

Re: [PATCH] xemit.c: fix a [-Wchar-subscripts] compiler warning

[sorry for duplicate]

Am 26.05.2016 um 01:06 schrieb Ramsay Jones:

Show 8 quoted lines

>
> While compiling on cygwin (x86_64), gcc complains thus:
>
>        CC xdiff/xemit.o
>    xdiff/xemit.c: In function ‘is_empty_rec’:
>    xdiff/xemit.c:163:2: warning: array subscript has type ‘char’ [-Wchar-subscripts]
>      while (len > 0 && isspace(*rec)) {
>      ^

Ah, it's not using our own isspace(), which works fine with signed chars, because it doesn't include git-compat-util.h. I'm spoilt by those char classifier macros that can be actually used with chars.. Thanks for catching!

René

patchxemit.c: fix a [-Wchar-subscripts] compiler warning