low-level

I'm trying to get a deeper understanding of how the low level operations of programming languages work and especially how they interact with the OS/CPU. I've probably read every answer in every stack/heap related thread here on Stack Overflow, and they are all brilliant. But there is still one thing that I didn't fully understand yet. Consider this function in pseudo code which tends to be valid Rust code ;-) fn foo() { let a = 1; let b = 2; let c = 3; let d = 4; // line X doSomething(a, b); doAnotherThing(c, d); } This is how I assume the stack to look like on line X: Stack a +-------------+

I'm slinging some C code and I need to bitshift a 32 bit int left 32 bits. When I run this code with the parameter n = 0, the shifting doesn't happen. int x = 0xFFFFFFFF; int y = x << (32 - n); Why doesn't this work? Shift at your own peril. Per the standard, what you want to do is undefined behavior . C99 §6.5.7 3 - The integer promotions are performed on each of the operands. The type of the result is that of the promoted left operand. If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined. In other words

If you had read my other question , you'll know I've spent this weekend putting together a 6502 CPU emulator as a programming exercise. The CPU emulator is mostly complete, and seems to be fairly accurate from my limited testing, however it is running incredibly fast, and I want to throttle it down to the actual clock speed of the machine. My current test loop is this: // Just loop infinitely. while (1 == 1) { CPU.ClockCyclesBeforeNext--; if (CPU.ClockCyclesBeforeNext <= 0) { // Find out how many clock cycles this instruction will take CPU.ClockCyclesBeforeNext = CPU.OpcodeMapper.Map[CPU

I read the following statement: The x86 architecture includes a specific segment type called the Task State Segment (TSS), to store hardware contexts. Although Linux doesn't use hardware context switches, it is nonetheless forced to set up a TSS for each distinct CPU in the system. I am wondering: Why doesn't Linux use the hardware support for context switch? Isn't the hardware approach much faster than the software approach? Is there any OS which does take advantage of the hardware context switch? Does windows use it? At last and as always, thanks for your patience and reply. -----------Added

I have a question for all the hardcore low level hackers out there. I ran across this sentence in a blog. I don't really think the source matters (it's Haack if you really care) because it seems to be a common statement. For example, many modern 3-D Games have their high performance core engine written in C++ and Assembly. As far as the assembly goes - is the code written in assembly because you don't want a compiler emitting extra instructions or using excessive bytes, or are you using better algorithms that you can't express in C (or can't express without the compiler mussing them up)? I