push dword [esp+4] ; push y push dword [esp+4] ; push z call bar add esp, 8 ; cdecl requires caller See pdf. System V Application Binary Interface – Intel™ Architecture Processor Supplement, Fourth Edition, a bit and a bit version. The bit version of standard can be found at and the 64bit version.
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Thu, 07 Dec If you are passing by value, and you only use the initial, passed-in struct one time, why shouldn’t the compiler recognize this and use the original struct rather than creating a new one? Comment 10 Alexandre Pereira Nunes The callee is free to modify the values during execution of the function, because the caller isn’t going to look at their values later.
I would assume that GCC modifying that parameter on the stack is fine, but I want to know where it is specified that it can do so. If you pass by value: I assumed that it was safe and wanted to avoid putting its value on the stack twice once to save and once for argument passing. Fri Sept 28 and beyond: R Samuel Klatchko A full zero for the whole homework or project if ANY of it was a cheat!
Post as a guest Name. Email me about changes to this bug report. Since it is very unlikely for gcc to default to 32bit stack alignment, it is highly recommended that functions should have stack aligned at bit before calling functions generated by gcc.
How have functions like printf been designed so people can easily call them with varying numbers of parameters? Comment 2 Richard Biener Miscellanous Web pages found via Google Official technology standards.
I understand perfectly that using structures like that is meant to be non-portable, but it’s quite handy to have something like that without too much worry about platforms, since altough I develop for several arches, almost all of them today have a gcc port, and I know there are others with similar issues.
linux – C calling conventions and passed arguments – Stack Overflow
Berry 1, 1 8 Any changes the called variable makes will be to the original variable in the calling program. Here’s the System V C calling conventions for i if you are curious. A compiler implements a set of calling conventions for other code and languages to operate with it in compiled code that is the essence of a calling convention and it is distinct from the C language itself, as it is a specific architecture implementation.
Comment 6 Alexandre Pereira Nunes You need to log in to change sbi386 bug’s status.
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So what I’m asking is: I was under the assumption that since the caller is the one that cleans them up, that they should contain the same values after the function call. That’s where I said the abi could change for several arches. Top of the stack is located easily.
In standard C, the callee can modify the values of its arguments all it wants, but the caller will never see the changes. See full activity log.
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Search “secondary sources” Textbooks and papers from by reputable publishers. How C code behaves and how the calling conventions work can be quite different. What may be confusing is that if one passes a POINTER to a value, then the callee can change that value by dereferencing the pointer, but if the callee actually changes the pointer itself the caller will not see that change.
Even TAs and profs can find them! Yes in practice an arguments might never actually be in any kind of stack, it would be in a named register this is especially true in platforms with a lot of registers – like MIPS. Ani386 callee is free to modify its arguments on the stack they are treated the same as local variables.
Comment 9 Richard Biener