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ASM: mixing assembler and C++

Posted 02-05-2012 at 12:05 PM by rainbowsally
Updated 08-06-2014 at 10:30 AM by rainbowsally

Tags asm, assembler, computer mad science

This is for intel 32 bit assembler. For 64-bits the calling convention is a bit different. See previous entries (specifically asm 64 bits) if you need a leg-up to break the 64 bit barrier.

Features:

Asm functions that can call class functions (using an object pointer) through jump vectors written in C.
Usage of extern "C" declarations to un-mangle names we need to keep simple for asm coding.

[If you really want to get down, you can use the mangled names as...

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ASM: Intercepting (and using) Errors (like segfaults) in asm (aka SEH)

Posted 02-03-2012 at 04:10 PM by rainbowsally

Tags asm, assembler, computer mad science, error handling, exceptions

This is for i86 and x86_64 types but with a bit of poking around you can probably find a similar way to do this with other CPUs.

Note: This asm requires 'sigaction'. (See the test code. And bear in mind that this is not an attempt to create a full-blown system of signal handlers. Check the libc docs for 'sigaction' for ideas on how you can use something like this for a seed for a more extensive application.)

There used to be a lot of cool little programs for the...

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ASM: 64 bit intel asm in linux

Posted 02-03-2012 at 04:01 PM by rainbowsally

Tags asm, assembler, computer mad science

If you're used to 32 bit asm in gcc, the 64 bit asm might throw you for a loop initially. That's because part of the stack is passed around in registers.

Let's compile a bit of test code and see what's going on.

If you're using our makefile-creator put this in a subdirectory named "src" or use whatever method you prefer if not.

file: src/main.c

Code:

// main.c
#include <stdio.h>

void  dbg(){}

...

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Assembler Stuff: Asm and Inline Asm

Posted 01-25-2012 at 07:15 PM by rainbowsally

Tags asm, assembler, computer mad science

Assembler Stuff: Asm and Inline Asm

Features:

Asm and inline asm examples
Using C macros to create global function names
Intel and ATT syntax
Viewing disassembly in a *.s file and using objdump

Let's get right to the point...

Code:

// main.c
// COMPILE: gcc main.c -o main --save-temps
// take a look at the C asm output file, 'main.s' afterwar

// 64 bit asm keeps part of the stack in registers in C, so let's
//

...

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Simple C: Filling in the blanks - A simple memory allocator/reallocator.

Posted 01-23-2012 at 07:32 AM by rainbowsally

Tags asm, memcat, memdup, simple c

No memdup()? No memcat()? No prob.

Today's Features:

Simple C/C++ program and new memdup() and memcat() functions.
C macros (spanning lines with backslash) to create 'lenient' aliases.
Type casting in C/C++ to override sometimes overly strict syntax checks.

Anyone that has used strdup() or strcat() knows how convenient those are. But when it comes to memory allocation and reallocation for other kinds of data the lack of simple standard mechanisms for this often leads to duplicated...

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