Empty struct value is passed differently in C and C++ on Intel386 and x86-64. Different compilers use different calling conventions on the same platform:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60336 The same compiler behaves different on different platforms: https://llvm.org/bugs/show_bug.cgi?id=26337 In some case, empty struct can't be passed in C++ at all: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60336 I am proposing to update Intel386, x86-64 and IA MCU psABIs to specify how to pass/return empty struct: 1. "collection". A collection is a structure, union or C++ class. 2. "empty collection". An empty collection is: a. A collection without member. Or b. A collection with only empty collections. Or c. An array of empty collections. 3. "empty record". An empty record is Plain Old Data (POD) for the purpose of layout and a. A collection without member. Or b. A collection with only empty collections. 4. No memory slot nor register should be used to pass or return an object of empty collection. The proposed Intel386, x86-64 and IA MCU psABIs are at https://github.com/hjl-tools/x86-psABI/wiki/X86-psABI Any comments? Thanks. -- H.J. _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
