Why does godbolt show parameter being passed in edi if C++ uses cdecl calling convention?
Why does godbolt (gcc 9.3) show parameter being passed in edi if C++ uses cdecl calling convention? I can't find anything on this
RBP and RSP are 64-bit registers, which means your code is being compiled for 64-bit, not 32-bit. cdecl is a 32-bit calling convention, it simply does not exist in 64-bit. On 64-bit systems, the first few integer-sized parameters are passed via registers, not the call stack.
On non-Windows platforms (godbolt runs on Amazon EC2 instances using Ubuntu), the first 6 integer-sized parameters are passed via the RDI, RSI, RDX, RCX, R8, and R9 registers, respectively. EDI is bytes 0-3 of RDI, and int is 4 bytes in your compiler, so you see the num parameter being passed via EDI.
On Windows platforms, the first 4 integer-sized parameters are passed via the RCX, RDX, R8, and R9 registers, respectively. EDI is not used for passing parameters.
See Stack frame layout on x86-64 for more details.
- Segmentation fault when converting char * to char **
- What's the difference between "C system calls" and "C library routines"?
- C standard - const qualification of struct members
- Conventions/good ways to initialize variables with default/NULL values
- why there are int56_t in clang c header file, and how to use them
- How to watch char values of strings pointed by a pointer to pointers in debugger mode of VSCode
- How to repeat a char using printf?
- Is left shifting a long long considered Undefined Behavior in C?
- String buffer gets skipped on the last loop iteration
- Unsigned int weird behavior with Loops in C
- How are Linked Lists implemented in the Ready Queue before moving onto the scheduler during the PCB implementation?
- How do C/C++/Objective-C compare with C# when it comes to using libraries?
- Why no switch on pointers?
- Similar syntax causes strange, repeated compile errors when building PHP from source on Windows
- Segmentation fault in C shellcode x64
- Where is the documentation for the XRandr header?
- i*=j ==x and i=i*j ==x behaving differently in C
- How can I make objcopy -Obinary append every text section?
- timespec equivalent for windows
- Register keyword: stack or heap
- Detect a parenthesized macro argument in C
- Modifying (stealing) Linux syscalls using kprobe
- Python's bz2 module not compiled by default
- ASCII file encoding with 16-bit bytes
- GtkContainer/GtkWidget maximum width
- AF-XDP: Implement Shared Umem sockets
- Are there known implementations of the CIEDE2000 or CIE94 Delta-E color difference calculation algorithm?
- ssh_channel_request_exec is not working without ssh_channel_read
- Are DHCP options ordered?
- Can't install apk using adb