将 int 变量的值赋给 int 指针

Question

I have the following C function used in an embedded software project . It's also used for the verification of the hardware and not in production.

void reg_read(int addr) {
   int result;
   int* reg_addr = (int*)(addr); // I cast the value of the addr variable to the reg_addr pointer hoping that it would point to the address stored in addr
   result = (*reg_addr); // this should trigger a read transaction on the AXI interface of the ARM CPU that I'm simulating
}
// later on...in the main function
reg_read(0x08000704);

The embedded software runs in a simulated environment(using QEMU+SystemC) and I can see if the AXI read transaction happens or not. In this case it doesn't happen.

However, if I assign a constant value to the pointer like int* reg_addr = (int*)0x08000704; then the AXI transaction happens.

I assume the compiler generates different instructions in each case. I also tried to declare reg_addr as volatile int* reg_addr; but it didn't work either.

Is there a portable and compliant way of casting the value of an int variable to an int pointer?

Answer 1

Your question is:

Is there a portable and compliant way of casting the value of an int variable to an int pointer?

There is not. Summed up from the comments:

Conversion of an integer to a pointer is implementation defined - Antti Haapala

It was suggested that you use uintptr_t or similar which is a good suggestion from Eugene Sh.

In the example of uintptr_t

uintptr_t = unsigned integer type capable of holding a pointer

From the vadefs.h file from the Microsoft Visual C++ header file vadefs.h it is defined as:

#ifdef _WIN64
    typedef unsigned __int64  uintptr_t;
#else
    typedef unsigned int uintptr_t;
#endif

In this manner, if you compile for x86 it would resolve to a 32bit data type and for x64, a 64 bit data type.