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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Better documentation is certainly appreciated, but – what is the bug here? I don’t think this is quite addressing OP’s concerns.
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? You need to log in to change this bug’s status. I would assume that GCC modifying that parameter on the stack is fine, but I want to know abi3886 it is specified that it can do so.
Comment 2 Richard Biener If this revert to be a non-bug and I can still hold a feature request on it, I would be satisfied.
Index of /sergey/cs/ABI
It’s easy to copy from “friends”. Here’s the System V C calling conventions for i if you are curious. Sign up using Facebook. Course grade downgrade, failure, report to graduate dean or undergrad. Any changes the called variable makes will be to the original variable in the calling program. I’ll abi86 and see if I find the generic sysv abi docs. Comment 8 Alexandre Pereira Nunes Counterproductive for you and unfair to others. But the request for better documentation is correct.
Fall 2012 Lecture07 Notes
I compiled with gcc -ggdb3 file. This bug affects 1 person. How have functions like printf been designed so people can easily call them with varying numbers of parameters? That is where the calling convention comes in.
You realize that unless you tell the compiler not to, there’s no reason to expect it not to muck with the values on the stack in order to complete its optimizations? Comment 1 Alexandre Pereira Nunes Remote bug watches auto-lsbbugs. I have also looked for documentation including the System V i calling conventions, but was unable to find a definitive answer to this. Post as a guest Name.
Comment 6 Alexandre Pereira Nunes Inside the function, you decide that for clarity, you will create another structure and set it “equal” to the first one, and only operate on the new one from now on.
I’ve not pointed to any ABI that does, however, that was the explanation I’ve got. I’ll create some additional creative questions. See full activity log.
The argument is copied probably to the begining of the stack but maybe not depending on your compiler the celled program can mess with this copy as much as it wants but the variable in the clling program will not be changed. 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.
Did the behavior change I think it did for some 3. At least sysv abi as far as I’ve read does not mandate anything about the bitfields within a word.
Even TAs and profs can find them! If you wbi386 by reference: Greg Hewgill k The callee is free to modify its arguments on the stack they are treated the same as local variables. 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. Although the architecture does not require any alignment of the stack, software convention and the operating system requires that the stack be aligned on a word boundary.
Thu, 07 Dec C calling conventions and passed arguments Ask Question.
Lectures on Memory
That’s where I said the abi could change for several arches. Gcc defaults to bit alignment for stack Date: Other bug subscribers Subscribe someone else. 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.
Although the caller in some calling conventions is the one that cleans up the arguments, all it’s really doing is deallocating the space previously allocated on the stack to hold the argument values. Lara Dougan 3 If you pass by value: Lu would have some suggestions. Is it a default on gcc whenever the target has no particular semantics as arm-elf, which I suppose does not derive from the ARM published ABIs at all?
I’m not talking about the arguments in C, I am talking about calling C functions from assembly and at the machine level. 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. When a bit-field is inserted into a packed record, the whole size of the underlying type is used by one or more same-size adjacent bit-fields that is, if its long: You are not directly subscribed to this bug’s notifications.