Add two macros for char*-based pointer arithmetic and use it in font.c

This fixes errornous pointer addition (+ on a short*), which crashed in some situation.
Fixes FS#12317 and should hopefully get the clips booting again.

Thanks to Jonathan Gordon for spotting the bad pointer arithmetic.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30724 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 2 insertions, 0 deletions

diff --git a/firmware/export/system.h b/firmware/export/system.h
index cec47f1a71..aa079940d1 100644
--- a/firmware/export/system.h
+++ b/firmware/export/system.h
@@ -124,6 +124,8 @@ int get_cpu_boost_counter(void);
     ptr = (typeof(ptr))tmp_ptr1; \
 }
 
+#define PTR_ADD(ptr, x) ((typeof(ptr))((char*)(ptr) + (x)))
+#define PTR_SUB(ptr, x) ((typeof(ptr))((char*)(ptr) - (x)))
 
 /* newer? SDL includes endian.h, So we ignore it */
 #if (CONFIG_PLATFORM & PLATFORM_HOSTED) || defined(__PCTOOL__)