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Hi, `x/x $ebx' on gdb/amd64 debugging inferior/i386 causes Cannot access memory at address 0xffffce70 (or so) as $ebx is considered `int' and sign-extended to 64-bit while the resulting address 0xffffffffffffce70 fails to be accessed. $esp does not exhibit this problem as it is `builtin_type_void_data_ptr' not `builtin_type_int' as $ebx is. Therefore it gets extended as unsigned. Simulate the part of paddress(); it is questionable how deep in the functions calling stack the address width cut should be. Regards, Jan As bugreported by John Reiser <jreiser(at)BitWagon.com>: When debugging a 32-bit executable on x86_64, gdb does not allow examining the stack if pointed to by a non-$esp register. For example, -----foo.S _start: .globl _start nop int3 movl %esp,%ebx int3 # examining memory from $ebx fails, from $esp succeeds nop nop ----- $ gcc -m32 -o foo -nostartfiles -nostdlib foo.S $ gdb foo Program received signal SIGTRAP, Trace/breakpoint trap. 0x08048076 in _start () (gdb) x/i $pc 0x8048076 <_start+2>: mov %esp,%ebx (gdb) stepi 0x08048078 in _start () (gdb) x/x $esp 0xffffce70: 0x00000001 (gdb) x/x $ebx 0xffffce70: Cannot access memory at address 0xffffce70 (gdb) x/x 0xffffce70 0xffffce70: 0x00000001 Expected Results: "x/x $ebx" should have succeeded, too, when %ebx has the same value as %esp and examining from $esp works.
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gdb-6.5-memory-address-width.patch
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