[LLVMdev] Accessing arguments in a caller

[Jordy Rose]

What I can think of:
1. Anonymous struct, to avoid a copy.
2. Use stdarg.h...dangerous but accomplishes what you're looking for.
3. Split up F: giant switch statements often indicate that your function is doing several different things. (IMHO...)
4. Don't worry about it, it's probably not a bottleneck. (Or rather, profile first...)

But no, there's no standard way to do this. Even C++11's variadic templates don't avoid the copy, and initializer lists are pretty much equivalent to an anonymous struct / const struct reference.

(Why not? Because calling conventions differ from platform to platform; often the first few arguments of a function are passed in registers, not on the stack.)

Jordy


On Aug 21, 2011, at 6:23, Carlo Alberto Ferraris wrote:

> Nella citazione giovedì 18 agosto 2011 09:11:36, Carlo Alberto Ferraris ha scritto:
>> I need some advice on "forwarding" arguments to a callee. Suppose I have a function F that is called at the beginning of all other functions in the module. From F I need to access (read) the arguments passed to its immediate caller. Right now I do something like boxing all arguments in the caller inside a struct and passing a pointer to the struct to F, alongside an identifier telling which caller F is being called from. F has then a giant switch that branches to the appropriate unboxing code. This is obviously suboptimal because I need to allocate the struct on the stack, copy the arguments inside of it and then passing an additional pointer to F.
>> I was wondering if there's a better way to do this, e.g. a way to access the stack frame of the caller (knowing, thanks to the identifier, which caller F was called from) or, more in general, arbitrary values d
> efined 
>> in the caller. Any suggestions?
> 
> Are there really no better ways of doing this?
> <cafxx.vcf>_______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev