Confusion with function pointers and callback execution order in C
I'm trying to debug I can't seem to get I'm getting frustrated with After trying multiple solutions online, I still can't figure this out..... Quick question that's been bugging me - I'm reviewing some code and I've been banging my head against this for hours... I'm working on a C program that involves multiple callbacks and function pointers, but I'm struggling to manage the execution order effectively. I have a structure that holds function pointers for different operations, and I want to ensure they execute in a specific sequence. Here’s a simplified version of my code: ```c #include <stdio.h> #include <stdlib.h> typedef void (*operation_fn)(void); typedef struct { operation_fn op1; operation_fn op2; } Operations; void firstOperation() { printf("First operation executed.\n"); } void secondOperation() { printf("Second operation executed.\n"); } void executeOperations(Operations *ops) { if (ops->op1) ops->op1(); if (ops->op2) ops->op2(); } int main() { Operations ops; ops.op1 = firstOperation; ops.op2 = secondOperation; executeOperations(&ops); return 0; } ``` When I run this code, it correctly executes both operations in the order I expect (first `firstOperation`, then `secondOperation`). However, if I change the order of the assignments in `main()` like so: ```c ops.op1 = secondOperation; ops.op2 = firstOperation; ``` I would expect the output to reflect this change, but instead, I see: ``` First operation executed. Second operation executed. ``` This has me puzzled, as it seems the function pointers are not being updated correctly. I've also verified that the function prototypes are consistent with their definitions. The question continues even if I explicitly set the function pointers to `NULL` before reassigning them. I've tried running this on both GCC 10.2 and clang 12.0 with the same result. What could I be missing here? Are there any common pitfalls with function pointers that I should be aware of? Any help would be appreciated! This is happening in both development and production on Ubuntu 20.04. Any help would be greatly appreciated! I'm working in a Linux environment. I'm working with C in a Docker container on Ubuntu 20.04. Thanks for taking the time to read this! I'm on CentOS using the latest version of C. Any examples would be super helpful. I'm working with C in a Docker container on Linux. Thanks, I really appreciate it! I recently upgraded to C 3.9.