I am looking at an assembly code that looks like the following:
cmp dword [rbp-0x4 {var_c}], 0x0
jne 0x12c0
To me, that reads:
Compare the value of something and null, and if there is no error (i.e. they match), jump to 0x12c0.
Is that correct? I don't understand what [rbp-0x4 {var_c}] is or why we would be comparing that to null.
I did try and follow a graph to learn what these variables were and I got the following:
0x4 = uint8_t file_class = 0x2var_c = In Set of Values {0, 1}rbp seems to be what is pushed in from mainAny help on understanding this would be appreciated. I am looking for clarification on what is being compared in the cmp statement.
Not quite, it's more:
Compare the value of something with zero and, if they are not equal, jump.
Assembly language has no concept of "null" and a cmp is generally the same as a sub (subtract) but without actually changing the value. Basically, it's:
Set the flags as if I had subtracted zero from something.
In more pseudo-code fashion, your two instructions amount to:
if var_c <> 0 then goto label_12c0
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