Is this actually an ABI requirement, or maybe it’s just some pessimization in certain scenarios? One example is System V Application Binary Interface AMD64 Architecture Processor Supplement. This ABI is for 64-bit x86-compatible CPUs (Linux x86_64 architecure). It is followed on Solaris, Linux, FreeBSD, macOS, Windows Subsystem for Linux: If a C++ object has either … Read more
In general, UNIX systems support backward binary compatibility (a binary built on an old machine continues to run on a newer one), but not the reverse. You can’t expect a binary built on a new system to run on an older one. STT_GNU_IFUNC is only the first of many problems you’ll encounter. If you need … Read more
Disclaimer, the following is not tested in production, use at your own risk. You can yourself release your library under dual ABI. This is more or less analogous to OSX “fat binary”, but built entirely with C++. The easiest way to do so would be to compile the library twice: with -D_GLIBCXX_USE_CXX11_ABI=0 and with -D_GLIBCXX_USE_CXX11_ABI=1. … Read more
Answer recommended by Intel
For small structs (eg point, rect) passing by value is perfectly acceptable. But, apart from speed, there is one other reason why you should be careful passing/returning large structs by value: Stack space. A lot of C programming is for embedded systems, where memory is at a premium, and stack sizes may be measured in … Read more
From “Intel®64 and IA-32 Architectures Optimization Reference Manual”, section 4.4.2: “For best performance, the Streaming SIMD Extensions and Streaming SIMD Extensions 2 require their memory operands to be aligned to 16-byte boundaries. Unaligned data can cause significant performance penalties compared to aligned data.” From Appendix D: “It is important to ensure that the stack frame … Read more
C defines no ABI. In fact, it bends over backwards to avoid defining an ABI. Those people, who like me, who have spent most of their programming lives programming in C on 16/32/64 bit architectures with 8 bit bytes, 2’s complement arithmetic and flat address spaces, will usually be quite surprised on reading the convoluted … Read more