Consider the following simple program:
.globl _start
.text
_start:
fldt val
.data
val: .byte 0x00,0x00,0x45,0x07,0x11,0x19,0x22,0xe9,0xfe,0xbf
With current GDB on x86-64 GNU/Linux hosts, after the moment the fldt
command has been executed the register st(0) looks like this,
according to the “info regs” output (TOP=7):
R7: Valid 0xffffffbffffffffeffffffe922191107450000 -0.910676542908976927
which is clearly wrong (just count its length). The problem is due to
the printf statement (see patch) printing a promoted integer value of
a char argument "raw[i]", and, since char is signed on x86-64
GNU/Linux, the erroneous “ffffff” are printed for the first three
bytes which turn out to be "negative". The fix is to use gdb_byte
instead which is unsigned (and is the type of value_contents(), the
type to be used for raw target bytes anyway). After the fix the value
will be printed correctly:
R7: Valid 0xbffee922191107450000 -0.910676542908976927
gdb/
2013-04-19 Vladimir Kargov <kargov@gmail.com>
Pedro Alves <palves@redhat.com>
* i387-tdep.c (i387_print_float_info): Use gdb_byte for pointer to
value contents.
gdb/testsuite/
2013-04-19 Vladimir Kargov <kargov@gmail.com>
Pedro Alves <palves@redhat.com>
* gdb.arch/i386-float.S: New file.
* gdb.arch/i386-float.exp: New file.
Pedro Alves