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https://bugs.gentoo.org/890302
https://bugzilla.redhat.com/1866474
https://sourceforge.net/p/dosemu/patches/129/
commit b3320c3a67c0bb050b40e76831ec95a4d156890a
Author: Matthew Ogilvie <mmogilvi+gnto@zoho.com>
Date: Thu Jun 15 21:55:30 2023 -0600
mem_base: avoid undefined behavior writing to const global with casts
Fix crash under gcc 10 or later.
--- a/src/arch/linux/mapping/mapping.c
+++ b/src/arch/linux/mapping/mapping.c
@@ -47,8 +47,8 @@ static int kmem_mappings = 0;
static struct mem_map_struct kmem_map[MAX_KMEM_MAPPINGS];
static int init_done = 0;
-unsigned char * const mem_base;
-char * const lowmem_base;
+unsigned char * mem_base;
+char * lowmem_base;
static struct mappingdrivers *mappingdrv[] = {
#ifdef HAVE_SHM_OPEN
@@ -205,7 +205,7 @@ void *alias_mapping(int cap, unsigned targ, size_t mapsize, int protect, void *s
addr = mappingdriver.alias(cap, target, mapsize, protect, source);
update_aliasmap(target, mapsize, (cap & MAPPING_VGAEMU) ? target : source);
if (cap & MAPPING_INIT_LOWRAM) {
- *(unsigned char **)&mem_base = addr;
+ mem_base = addr;
}
return addr;
}
@@ -416,7 +416,7 @@ void *alloc_mapping(int cap, size_t mapsize, off_t target)
if (cap & MAPPING_INIT_LOWRAM) {
Q__printf("MAPPING: LOWRAM_INIT, cap=%s, base=%p\n", cap, addr);
- *(char **)(&lowmem_base) = addr;
+ lowmem_base = addr;
}
return addr;
}
--- a/src/include/memory.h
+++ b/src/include/memory.h
@@ -209,7 +209,7 @@ void *lowmemp(const void *ptr);
restrictions it can be non-zero. Non-zero values block vm86 but at least
give NULL pointer protection.
*/
-extern unsigned char * const mem_base;
+extern unsigned char * mem_base;
/* lowmem_base points to a shared memory image of the area 0--1MB+64K.
It does not have any holes or mapping for video RAM etc.
@@ -221,7 +221,7 @@ extern unsigned char * const mem_base;
It is set "const" to help GCC optimize accesses. In reality it is set only
once, at startup
*/
-extern char * const lowmem_base;
+extern char * lowmem_base;
#define UNIX_READ_BYTE(addr) (*(Bit8u *) (addr))
#define UNIX_WRITE_BYTE(addr, val) (*(Bit8u *) (addr) = (val) )
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