Re: char * vs. const char *

[Robert Wilhelm <robert physiol med tu-muenchen de>]

On Tue, Mar 03, 1998 at 01:46:53PM -0600, Federico Mena wrote:
> >  Would it make sense to chage this to 
> >  gnome_pixmap_new_from_file (const char *filename) ?
> >  Note that quite a few function iprototypes down to imlib would need to be changed.
> 
> I wouldn't mind such a change.  If you think it is useful, feel free
> to do it.
> 
>   Quartic
> 
>

I have appended a patch. It would be nice if someone with cvs write access
could check it in.

Note that there are two new warnings are introduced with this patch:
 
gcc -DHAVE_CONFIG_H -I. -I. -I.. -I.. -I./.. -I/usr/local/include -I/usr/X11R6/include -g -O2 -c -fPIC -DPIC gnome-pixmap.c
gnome-pixmap.c: In function `load_file':
gnome-pixmap.c:344: warning: passing arg 1 of `gdk_imlib_load_image' discards `const' from pointer target type
gnome-pixmap.c: In function `load_pixmap':
gnome-pixmap.c:494: warning: passing arg 2 of `g_hash_table_lookup' discards `const' from pointer target type


I will make a smilar patch to imlib soon to fix the first warning.
The second warning looks like a gcc flaw, because g_hash_table_lookup() takes
a const gpointer.

I have made a small test case. Maybe some C guru can comment on it.
snoopy$ cat  g.c


typedef void* gpointer;

gpointer    g    (const gpointer);
gpointer    g2   (const void *);

void f(const char *file)
{
        gpointer pit;

        pit = g ( file );
        pit = g2( file );
}
snoopy$ gcc -c  g.c
g.c: In function `f':
g.c:12: warning: passing arg 1 of `g' discards `const' from pointer target type
snoopy:~/SRC/gnome/work/gnome-libs/libgnomeui$


Robert

diff -ur cvs/gnome-libs/ChangeLog work/gnome-libs/ChangeLog
--- cvs/gnome-libs/ChangeLog	Wed Mar  4 11:45:23 1998
+++ work/gnome-libs/ChangeLog	Wed Mar  4 15:13:51 1998
@@ -1,3 +1,9 @@
+Wed Mar  4 15:12:59 1998  Robert Wilhelm  <robert@snoopy.physiol.med.tu-muenchen.de>
+
+	* libgnome/gnome-util.h: 
+	* libgnome/gnome-util.c: 
+	(g_file_exists): added const to parameter.
+
 Wed Mar  4 01:06:58 1998  Tom Tromey  <tromey@cygnus.com>
 
 	* acconfig.h (HAVE_PROGRAM_INVOCATION_SHORT_NAME,
diff -ur cvs/gnome-libs/libgnome/gnome-util.c work/gnome-libs/libgnome/gnome-util.c
--- cvs/gnome-libs/libgnome/gnome-util.c	Tue Mar  3 10:10:20 1998
+++ work/gnome-libs/libgnome/gnome-util.c	Wed Mar  4 14:23:16 1998
@@ -119,11 +119,11 @@
 	return (gnome_dirrelative_file (GNOMEDATADIR, "share", filename, TRUE));
 }
 
-/* DOC: g_file_exists (char *filename)
+/* DOC: g_file_exists (const char *filename)
  * Returns true if filename exists
  */
 int
-g_file_exists (char *filename)
+g_file_exists (const char *filename)
 {
 	struct stat s;
 	
diff -ur cvs/gnome-libs/libgnome/gnome-util.h work/gnome-libs/libgnome/gnome-util.h
--- cvs/gnome-libs/libgnome/gnome-util.h	Tue Mar  3 10:10:20 1998
+++ work/gnome-libs/libgnome/gnome-util.h	Wed Mar  4 14:23:38 1998
@@ -12,7 +12,7 @@
 char *gnome_unconditional_libdir_file (char *filename);
 char *gnome_unconditional_datadir_file (char *filename);
 char *gnome_unconditional_pixmap_file (char *filename);
-int   g_file_exists (char *filename);
+int   g_file_exists (const char *filename);
 char *g_copy_strings (const char *first, ...);
 char *g_unix_error_string (int error_num);
 char *g_concat_dir_and_file (const char *dir, const char *file);
diff -ur cvs/gnome-libs/libgnomeui/ChangeLog work/gnome-libs/libgnomeui/ChangeLog
--- cvs/gnome-libs/libgnomeui/ChangeLog	Wed Mar  4 11:45:29 1998
+++ work/gnome-libs/libgnomeui/ChangeLog	Wed Mar  4 15:12:39 1998
@@ -1,3 +1,18 @@
+Wed Mar  4 15:03:52 1998  Robert Wilhelm  <robert@physiol.med.tu-muenchen.de>
+
+	* gnome-pixmap.h:
+	* gnome-pixmap.c: (gnome_pixmap_new_from_file): added const
+ 	to filename parameter.
+        (gnome_pixmap_new_from_file_at_size): Likewise.
+	(load_file): Likewise.
+	(gnome_pixmap_load_file): Likewise.
+	(gnome_pixmap_load_file_at_size): Likewise.
+	(load_pixmap): Likewise.
+	(gnome_create_pixmap_gdk): Likewise.
+	(gnome_create_pixmap_gtk): Likewise.
+	(gnome_create_pixmap_widget): Likewise.
+	(gnome_set_pixmap_widget): Likewise.
+	
 Wed Mar  4 00:14:01 1998  Miguel de Icaza  <miguel@nuclecu.unam.mx>
 
 	* gtk-ted.c (gtk_ted_new_layout): create widgets with an argument
diff -ur cvs/gnome-libs/libgnomeui/gnome-pixmap.c work/gnome-libs/libgnomeui/gnome-pixmap.c
--- cvs/gnome-libs/libgnomeui/gnome-pixmap.c	Sun Mar  1 17:40:45 1998
+++ work/gnome-libs/libgnomeui/gnome-pixmap.c	Wed Mar  4 13:35:46 1998
@@ -109,7 +109,7 @@
 }
 
 GtkWidget *
-gnome_pixmap_new_from_file (char *filename)
+gnome_pixmap_new_from_file (const char *filename)
 {
 	GnomePixmap *gpixmap;
 
@@ -120,7 +120,7 @@
 }
 
 GtkWidget *
-gnome_pixmap_new_from_file_at_size (char *filename, int width, int height)
+gnome_pixmap_new_from_file_at_size (const char *filename, int width, int height)
 {
 	GnomePixmap *gpixmap;
 
@@ -335,7 +335,7 @@
 }
 
 static void
-load_file (GnomePixmap *gpixmap, char *filename, int scaled, int width, int height)
+load_file (GnomePixmap *gpixmap, const char *filename, int scaled, int width, int height)
 {
 	GdkImlibImage *im;
 
@@ -370,7 +370,7 @@
 }
 
 void
-gnome_pixmap_load_file (GnomePixmap *gpixmap, char *filename)
+gnome_pixmap_load_file (GnomePixmap *gpixmap, const char *filename)
 {
 	g_return_if_fail (gpixmap != NULL);
 	g_return_if_fail (GNOME_IS_PIXMAP (gpixmap));
@@ -380,7 +380,7 @@
 }
 
 void
-gnome_pixmap_load_file_at_size (GnomePixmap *gpixmap, char *filename, int width, int height)
+gnome_pixmap_load_file_at_size (GnomePixmap *gpixmap, const char *filename, int width, int height)
 {
 	g_return_if_fail (gpixmap != NULL);
 	g_return_if_fail (GNOME_IS_PIXMAP (gpixmap));
@@ -485,7 +485,7 @@
 }
 
 static void
-load_pixmap(GdkWindow *window, GdkPixmap **pixmap, GdkBitmap **mask, GdkColor *transparent, char *filename)
+load_pixmap(GdkWindow *window, GdkPixmap **pixmap, GdkBitmap **mask, GdkColor *transparent, const char *filename)
 {
 	struct pixmap_item *pit;
 
@@ -505,7 +505,7 @@
 }
 
 void
-gnome_create_pixmap_gdk (GdkWindow *window, GdkPixmap **pixmap, GdkBitmap **mask, GdkColor *transparent, char *file)
+gnome_create_pixmap_gdk (GdkWindow *window, GdkPixmap **pixmap, GdkBitmap **mask, GdkColor *transparent, const char *file)
 {
 	g_assert(window != NULL);
 	g_assert(pixmap != NULL);
@@ -522,7 +522,7 @@
 }
 
 void
-gnome_create_pixmap_gtk (GtkWidget *window, GdkPixmap **pixmap, GdkBitmap **mask, GtkWidget *holder, char *file)
+gnome_create_pixmap_gtk (GtkWidget *window, GdkPixmap **pixmap, GdkBitmap **mask, GtkWidget *holder,  const char *file)
 {
 	GtkStyle *style;
 	
@@ -567,7 +567,7 @@
 }
 
 GtkWidget *
-gnome_create_pixmap_widget (GtkWidget *window, GtkWidget *holder, char *file)
+gnome_create_pixmap_widget (GtkWidget *window, GtkWidget *holder, const char *file)
 {
 	GdkPixmap *pixmap;
 	GdkBitmap *mask;
@@ -592,7 +592,7 @@
 }
 
 void
-gnome_set_pixmap_widget (GtkPixmap *pixmap, GtkWidget *window, GtkWidget *holder, gchar *file)
+gnome_set_pixmap_widget (GtkPixmap *pixmap, GtkWidget *window, GtkWidget *holder, const char *file)
 {
 	GdkPixmap *gpixmap;
 	GdkBitmap *mask;
diff -ur cvs/gnome-libs/libgnomeui/gnome-pixmap.h work/gnome-libs/libgnomeui/gnome-pixmap.h
--- cvs/gnome-libs/libgnomeui/gnome-pixmap.h	Tue Feb 24 05:40:09 1998
+++ work/gnome-libs/libgnomeui/gnome-pixmap.h	Wed Mar  4 13:35:50 1998
@@ -31,8 +31,8 @@
 
 guint      gnome_pixmap_get_type               (void);
 
-GtkWidget *gnome_pixmap_new_from_file          (char *filename);
-GtkWidget *gnome_pixmap_new_from_file_at_size  (char *filename, int width, int height);
+GtkWidget *gnome_pixmap_new_from_file          (const char *filename);
+GtkWidget *gnome_pixmap_new_from_file_at_size  (const char *filename, int width, int height);
 GtkWidget *gnome_pixmap_new_from_xpm_d         (char **xpm_data);
 GtkWidget *gnome_pixmap_new_from_xpm_d_at_size (char **xpm_data, int width, int height);
 GtkWidget *gnome_pixmap_new_from_rgb_d         (unsigned char *data, unsigned char *alpha,
@@ -41,8 +41,8 @@
 						int rgb_width, int rgb_height,
 						int width, int height);
 
-void       gnome_pixmap_load_file              (GnomePixmap *gpixmap, char *filename);
-void       gnome_pixmap_load_file_at_size      (GnomePixmap *gpixmap, char *filename, int width, int height);
+void       gnome_pixmap_load_file              (GnomePixmap *gpixmap, const char *filename);
+void       gnome_pixmap_load_file_at_size      (GnomePixmap *gpixmap, const char *filename, int width, int height);
 void       gnome_pixmap_load_xpm_d             (GnomePixmap *gpixmap, char **xpm_data);
 void       gnome_pixmap_load_xpm_d_at_size     (GnomePixmap *gpixmap, char **xpm_data, int width, int height);
 void       gnome_pixmap_load_rgb_d             (GnomePixmap *gpixmap, unsigned char *data, unsigned char *alpha,
@@ -63,12 +63,12 @@
 					   GdkPixmap **pixmap,
 					   GdkBitmap **mask,
 					   GdkColor  *transparent,
-					   char *file);
+					   const char *file);
 void gnome_create_pixmap_gtk              (GtkWidget *window,
 					   GdkPixmap **pixmap,
 					   GdkBitmap **mask,
 					   GtkWidget *holder,
-					   char *file);
+					   const char *file);
 void gnome_create_pixmap_gtk_d            (GtkWidget *window,
 					   GdkPixmap **pixmap,
 					   GdkBitmap **mask,
@@ -76,14 +76,14 @@
 					   char **data);
 GtkWidget *gnome_create_pixmap_widget     (GtkWidget *window,
 					   GtkWidget *holder,
-					   char *file);
+					   const char *file);
 GtkWidget *gnome_create_pixmap_widget_d   (GtkWidget *window,
 					   GtkWidget *holder,
 					   char **data);
 void gnome_set_pixmap_widget              (GtkPixmap *pixmap,	
 					   GtkWidget *window,
 					   GtkWidget *holder,
-					   char *file);
+					   const char *file);
 void gnome_set_pixmap_widget_d            (GtkPixmap *pixmap,	
 					   GtkWidget *window,
 					   GtkWidget *holder,