2 ms·

Interesting suggestions. How do you "hook' a function, like you said about malloc,free, main and exit? I guess it means intercept calls to it and do something

Interesting suggestions. How do you "hook' a function, like you said about malloc,free, main and exit? I guess it means intercept calls to it and do something additional to what it already does, something like Python decorators, but how do you do it in C or C++? I used C a lot (but not C++), but much earlier, and don't remember any method of hooking. atexit(), or something like it?

tsimionescu 3y ago
Given that they mention ifdef, I guess they just mean something like `#define malloc(x) (tracing_malloc((x))) ` in every place except the one where the tracing version is defined.
- fsckboy 3y ago
  hungarian standardizes procedure/function names anyway (typed and capitalized), so while you're changing the name, it gives you "a place to stand" to do the other things you want to do. for normal/average operating environments, I prefer to just indirect through an extra procedure call, gives you a place to put a breakpoint, and then if you need streamlined performant code you can #define it all away. But, if you plan to #define it all away, make sure that is a regular part of your work flow beforehand. you can have a procedure version, a heavyweight define and a lightweight define (and use your defines inside your procedure to test them there). On a regular basis you need to make sure your infrastructure is all doing what you think it is. Same is true for main(), use it for setting up infrastructure, have it call Main() which is "your main". if you are on a large enough project you can budget time for tools, the actual "__main.asm" code that calls C main() is also accessible and you can hook away in there too. Have to do it for all compilers, and track compilers, but on the scale of a large project, that's not the end of the world.
- Conscat 3y ago
  Why do that with the preprocessor rather than the `--wrap` flag? That's what most malloc libraries do.

tsimionescu 3y ago

Given that they mention ifdef, I guess they just mean something like `#define malloc(x) (tracing_malloc((x))) ` in every place except the one where the tracing version is defined.

fsckboy 3y ago
hungarian standardizes procedure/function names anyway (typed and capitalized), so while you're changing the name, it gives you "a place to stand" to do the other things you want to do. for normal/average operating environments, I prefer to just indirect through an extra procedure call, gives you a place to put a breakpoint, and then if you need streamlined performant code you can #define it all away. But, if you plan to #define it all away, make sure that is a regular part of your work flow beforehand. you can have a procedure version, a heavyweight define and a lightweight define (and use your defines inside your procedure to test them there). On a regular basis you need to make sure your infrastructure is all doing what you think it is. Same is true for main(), use it for setting up infrastructure, have it call Main() which is "your main". if you are on a large enough project you can budget time for tools, the actual "__main.asm" code that calls C main() is also accessible and you can hook away in there too. Have to do it for all compilers, and track compilers, but on the scale of a large project, that's not the end of the world.
Conscat 3y ago
Why do that with the preprocessor rather than the `--wrap` flag? That's what most malloc libraries do.