From e8c7950a17b7821eff628e191727b13869cddbb2 Mon Sep 17 00:00:00 2001
From: Mamoru TASAKA <mtasaka@fedoraproject.org>
Date: Sun, 23 Aug 2020 16:21:55 +0900
Subject: [PATCH] memory.h: don't mark pointer to be modified as const

https://bugzilla.redhat.com/show_bug.cgi?id=1866474
https://bugzilla.rpmfusion.org/show_bug.cgi?id=5663

Pointers to be modified cannot be declared as "const *". gcc10 defaults to -fno-common,
and with this flag, trying to modify "const *" pointer variable causes segfault.
---
 src/arch/linux/mapping/mapping.c | 4 ++--
 src/include/memory.h             | 7 ++-----
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/arch/linux/mapping/mapping.c b/src/arch/linux/mapping/mapping.c
index 1d6c0725..19055434 100644
--- a/src/arch/linux/mapping/mapping.c
+++ b/src/arch/linux/mapping/mapping.c
@@ -58,8 +58,8 @@ 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;
 #ifndef HAVE_MREMAP_FIXED
 int have_mremap_fixed = 1;
 #endif
diff --git a/src/include/memory.h b/src/include/memory.h
index a5d6e96a..3d362a07 100644
--- a/src/include/memory.h
+++ b/src/include/memory.h
@@ -213,7 +213,7 @@ 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.
@@ -221,11 +221,8 @@ extern unsigned char * const mem_base;
    DOSEMU writes will not be trapped. This allows easy interference with
    simx86, NULL page protection, and removal of the VGA protected memory
    access hack.
-
-   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) )
-- 
2.26.2