In C++ the bit representation (and even the size) of a bool is implementation defined; generally it’s implemented as a char-sized type taking 1 or 0 as possible values. If you set its value to anything different from the allowed ones (in this specific case by aliasing a bool through a char and modifying its … 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
An ABI (Application Binary Interface) is a standard that defines a mapping between low-level concepts in high-level languages and the abilities of a specific hardware/OS platform’s machine code. That includes things like: how C/C++/Fortran/… data types are laid out in memory (data sizes / alignments) how nested function calls work (where and how the information … Read more
Many modern Android devices (i.e. Nexus 5x) have AArch64 processors with arm64-v8a instruction set. Both – armeabi and armeabi-v7a – libraries run fine on these modern devices. Therefore, we can assume the answer to your question to be ‘YES’. See this for a breakdown of ABI management on Android: https://developer.android.com/ndk/guides/abis.html
Here’s the complete table of registers and their use from the documentation [PDF Link]: r12, r13, r14, r15, rbx, rsp, rbp are the callee-saved registers – they have a “Yes” in the “Preserved across function calls” column.
Hans and DarkDust answer covered i386/i686 and amd64/x86_64, so there’s no sense in revisiting them. This answer will focus on X32, and provide some info learned after a X32 port. x32 is an ABI for amd64/x86_64 CPUs using 32-bit integers, longs and pointers. The idea is to combine the smaller memory and cache footprint from … Read more
TL:DR: int 0x80 works when used correctly, as long as any pointers fit in 32 bits (stack pointers don’t fit). But beware that strace decodes it wrong unless you have a very recent strace + kernel. int 0x80 zeros r8-r11 for reasons, and preserves everything else. Use it exactly like you would in 32-bit code, … Read more
The default installed NDK doesn’t seem to have the tools required to strip binaries that have been built with ARMEABI support, so it ends up packaging the whole library, which increases the built file size substantially. I’ve found that installing the “NDK (Side by side)” tool from Android Studio -> Tools -> SDK Manager -> … Read more
Caller-saved registers (AKA volatile registers, or call-clobbered) are used to hold temporary quantities that need not be preserved across calls. For that reason, it is the caller’s responsibility to push these registers onto the stack or copy them somewhere else if it wants to restore this value after a procedure call. It’s normal to let … Read more
The System V AMD64 psABI document is maintained as LaTeX sources on GitLab. Similarly the i386 psABI is a separate GitLab repo. (Formerly on github). Those pages have info on where revisions are discussed. The x32 ABI (32-bit pointers in long mode) is part of the x86-64 aka AMD64 ABI doc. See Chapter 10: ILP32 … Read more