When you’re staring at a wall of disassembly in IDA Pro, the first skill that pays dividends is recognizing the shape of common C control flow structures after the compiler has had its way with them.
The if/else Pattern
The most basic pattern: a conditional jump (je, jne, jl, jg, etc.) followed by two diverging code blocks that reconverge at a common point. The key tell is the unconditional jmp at the end of the “true” branch that skips over the “false” branch.
cmp eax, 5
jne .false_branch
; true branch code here
jmp .merge
.false_branch:
; false branch code here
.merge:
The compiler may invert the condition — if your C code says if (x == 5), the disassembly might use jne to jump past the true branch. This is normal. Read the structure, not the condition.
For Loops
A classic for loop compiles to an initializer block, a condition check at the top (or bottom, depending on optimization level), the loop body, an increment, and a backward jump.
More to come as I work through the BTL2 material…