Igor’s tip of the week #71: Decompile as call

Although the Hex-Rays decompiler was originally written to deal with compiler-generated code, it can still do a decent job with manually written assembly. However, such code may use non-standard instructions or use them in non-standard ways, in which case the decompiler may fail to produce equivalent C code and has to fall back to _asm […]

Igor’s tip of the week #69: Split expression

While using the decompiler, sometimes you may have seen the item named Split expression in the context menu. What does it do and where it can be useful? Let’s look at two examples where it can be applied. Structure field initialization Modern compilers perform many optimizations to speed up code execution. One of them is merging two […]

Igor’s tip of the week #68: Skippable instructions

In compiled code, you can sometimes find instructions which do not directly represent the code written by the programmer but were added by the compiler for its own purposes or due to the requirements of the environment the program is executing in. Skippable instruction kinds Compiled functions usually have  prolog instructions at the start which perform various […]

Igor’s tip of the week #67: Decompiler helpers

We’ve already described custom types used in the decompiled code, but you may also encounter some unusual keywords resembling function calls. They are used by the decompiler to represent operations which it was unable to map to nice C code, or just to make the output more compact. They are listed in the defs.h […]

Igor’s tip of the week #66: Decompiler annotations

When working with pseudocode in the decompiler, you may have noticed that variable declarations and hints have comments with somewhat cryptic contents. What do they mean? While meaning of some may be obvious, others less so, and a few appear only in rare situations. Variable location The fist part of the comment is the variable location. For stack […]

Igor’s tip of the week #56: String literals in pseudocode

Strings in binaries are very useful for the reverse engineer: they often contain messages shown to the user, or sometimes even internal debugging information (function or variable names) and so having them displayed in the decompiled code is very helpful. However, sometimes you may see named variables in pseudocode even though the disassembly shows the string […]

Igor’s tip of the week #54: Shifted pointers

Previously we briefly mentioned shifted pointers but without details. What are they? Shifted pointers is another custom extension to the C syntax. They are used by IDA and decompiler to represent a pointer to an object with some offset or adjustment (positive or negative). Let’s see how they work and several situations where they can […]