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Re: MIPS 3.4.0 ABI and one-sized arrays

Eric Botcazou wrote:
Strictly speaking, I don't think so. Take a look at the second line in the document, I see no mention of arrays.

The C language, and related languages, have no mechanism for passing arrays as arguments or returning them as return values. In both cases, they decay to simple pointers. Most gcc developers have C or C++ as their main language. Thus, when people talk about aggregate parameters and return values, they sometimes assume that only structs and unions are affected, because they do not know of any way for arrays to be affected. The intent here is to cover all aggregate types, including arrays.

You can find the SGI published ABI here:
Or just visit, click on Irix6 Developer, and then MIPSPro N32 ABI Handbook.

On page 7, it says "Structs, unions, or other composite types ...". A little later it says "Array fields of structs are passed like unions. Array parameters are passed by reference (unless the relevant language standard requires otherwise)." So it looks like we need two different mechanisms for passing arrays, depending on whether they are structure fields or standalone objects.

Since we can't write C/C++ testcases that have array parameters, it isn't possible for C/C++ developers to have gotten this part of the ABI correct.
Jim Wilson, GNU Tools Support,

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