Extending C with cmacro

The following toy implementation of coroutines shows how to execute an arbitrary function as a coroutine. The idea is that if the coroutine invocation performs the context switch to the new coroutine straight away, it can use C compiler to put the arguments on the stack and the library doesn't have to handle it itself. Of course, given that coroutines are executed concurrently, any non-void return value is lost.

The behavior of malloc(0) is implementation defined by the standard. The two legal possibilities are to return a null pointer or a unique pointer. In many implementations, the second option is accomplished by means of internally increasing the length to 1 (which is then likely rounded up to 16 or so). Legally, one cannot deference this pointer, although in practice some bytes are allocated which means that won’t crash.

This is for people who want to understand how programs get loaded under linux. In particular it talks about dynamically loaded x86 ELF files. The information you learn will let you understand how to debug problems that occur in your program before main starts up.

American fuzzy lop is a security-oriented fuzzer that employs a novel type of compile-time instrumentation and genetic algorithms to automatically discover clean, interesting test cases that trigger new internal states in the targeted binary. This substantially improves the functional coverage for the fuzzed code. The compact synthesized corpora produced by the tool are also useful for seeding other, more labor- or resource-intensive testing regimes down the road.

Back in the day, I was reading a book about UNIX® programming and have learned how to write a signal handler. It was a long time ago and I don’t remember the book, but to this day the way described in that book is something that shows up in Google’s top results when you search for “How to write a signal handler”. Here it is — a simple, elegant solution to the world’s toughest problem:

In this document we will take a look at how to map various classic high-level programming language constructs to LLVM IR. The purpose of the document is to make the learning curve less steep for aspiring LLVM users.

Merge sort is a wonderful, widely used sorting algorithm, with consistent data-independent performance. When not in-place merge sorting, that is when the source and destination array are not the same, performance is O(nlgn). When in-place, so the source and destination array are the same, performance is slightly slower: O(nlg2n). Because not-in-place sorting algorithms are faster, implementations frequently allocate memory for the destination array, copy the sorted result back into the source array, and proceed to deallocate the destination array. STL uses this type of a strategy to construct a fast in-place sort from a faster not-in-place sort whenever memory is available. Of course, when memory is not available, in-place sort is necessary, and STL also provides such an implementation.

In cryptographic applications, it is often useful to wipe data from memory once it is no longer needed. In a perfect world, this is unnecessary since nobody would gain unauthorized access to that data; but if someone is able to exploit an unrelated problem — a vulnerability which yields remote code execution, or a feature which allows uninitialized memory to be read remotely, for example — then ensuring that sensitive data (e.g., cryptographic keys) is no longer accessible will reduce the impact of the attack. In short, zeroing buffers which contained sensitive information is an exploit mitigation technique.

bin2c - A simple utility for converting a binary file to a c application which
can then be included within an application.

The idea of transactional memory is to create a block of a code that will be executed 'atomically'. Thanks to this abstraction, the creation of a concurent program is a bit easier. Indeed, it avoids the usage of locks to protect a shared data-structure or variable. This block delimits the start and the commit of the transaction.

C library to restrict resources access and to perform basic profiling on subprocesses.

C99 introduced the concept of designated initializers, that allows to initialize a structure using the name of the fields, like this:

struct {int x, float y} MyStruct;
MyStruct a = {
.x = 10,
.y = 3.6,
};

Here is a C macro that extends this syntax to function calls.