CODEWITHSUNDEEP
gdb
Zazaeil
Zazaeil

Reputation: 4109

How to set exact instruction `gdb` puts a breakpoint on?

Given code like that (assume line number is x):

if (condition) return false;

...if b x is used to set breakpoint at that line, it would break on condition evaluation. How do I instruct gdb to put breakpoint on the same line but different instruction? In my case target is return false.

Upvotes: 0

Views: 92

Answers (1)

Employed Russian
Employed Russian

Reputation: 213375

How do I

You can set a breakpoint on any instruction you want with b *0x1234 syntax. Example:

(gdb) disas $pc
Dump of assembler code for function main:
=> 0x0000555555555040 <+0>:     xor    %eax,%eax
   0x0000555555555042 <+2>:     cmp    $0x1,%edi
   0x0000555555555045 <+5>:     setg   %al
   0x0000555555555048 <+8>:     retq   
End of assembler dump.
(gdb) b *0x0000555555555045
Breakpoint 2 at 0x555555555045
(gdb) c
Continuing.

Breakpoint 2, 0x0000555555555045 in main ()
(gdb) x/i $pc
=> 0x555555555045 <main+5>:     setg   %al

Upvotes: 1

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