M2-Planet/known_issues.org

M2-Planet is subset of the C programming language.

Mostly by eliminating features that have yet to be proven useful in building compilers, linkers or assemblers.

* AMD64 & AArch64 int initialization wrong
right now the code in cc_core.c in the function void program() simply doesn't output the correct output for AArch64 or AMD64.
As the function should numerate the string global_token to determine if the leading 32bits should be 0 or 0xFFFFFFFF and output %0 or %0xFFFFFFFF accordingly.

** example of failing code
#include<stdlib.h>
#include<stdio.h>
#include<string.h>

void write_string(char* s, FILE* f)
{
	while(0 != s[0])
	{
		fputc(s[0], f);
		s = s + 1;
	}
}

void* empty = 0;

int main()
{
	if (0 == empty)
	{
		write_string("Yes, is empty\n", stdout);
	}
	else
	{
		write_string("Oops, why not?\n", stdout);
	}
	return 0;
}

* Pointer arithmetic wrong
It isn't uncommon for complex C programs to iterate over an array using a pointer.

** example of failing code
#include <stdio.h>
#include <stdlib.h>

void walk_array(char** array, char** array_end)
{
	char** i = array;
	while(i < array_end)
	{
		fputs(i[0], stdout);
		fputc('\n', stdout);
		i = i + 1;
	}
}

int main()
{
	char** array = calloc(10, sizeof(char*));
	array[0] = "hello";
	array[1] = "world";
	array[2] = "how";
	array[3] = "are";
	array[4] = "you";
	array[5] = "today";
	array[6] = "I";
	array[7] = "am";
	array[8] = "doing";
	array[9] = "fine";
	walk_array(array, array + 10);
	return 0;
}

** work around code
#include <stdio.h>
#include <stdlib.h>

#if defined(__M2__)
	#define pointer_size sizeof(char*)
#else
	#define pointer_size 1
#endif

void walk_array(char** array, char** array_end)
{
	char** i = array;
	while(i < array_end)
	{
		fputs(i[0], stdout);
		fputc('\n', stdout);
		i = i + pointer_size;
	}
}

int main()
{
	char** array = calloc(10, sizeof(char*));
	array[0] = "hello";
	array[1] = "world";
	array[2] = "how";
	array[3] = "are";
	array[4] = "you";
	array[5] = "today";
	array[6] = "I";
	array[7] = "am";
	array[8] = "doing";
	array[9] = "fine";
	walk_array(array, array + (10 * pointer_size));
	return 0;
}

* struct initialization
M2-Planet doesn't support static initialization for structs yet.

Simply because time hasn't been made available for the effort.

Patches for adding support are welcome.

* C style function pointers
M2-Planet supports universal function pointer FUNCTION
Simply delete the typedef and the code works fine in M2-Planet

** example of failing code
#include <stdio.h>
typedef int (*FUNCTION) ();

struct function
{
	FUNCTION function;
	int arity;
	char* name;
};

struct function fun_make_cell_;

int make_cell_ ()
{
	char* i = fun_make_cell_.name;
	while(0 != i[0])
	{
		fputc(i[0], stdout);
		i = i + 1;
	}
	return fun_make_cell_.arity;
}

int main ()
{
	fun_make_cell_.function = make_cell_;
	fun_make_cell_.arity = 2;
	fun_make_cell_.name = "bar\n";
	fun_make_cell_.function();
}

* logical and do not short circuit
Both sides of && evaluate because it hasn't been shown to be worth the effort of implementation of short-circuit logic

** example of failing code
#include <stdlib.h>
#include <stdio.h>

int boom()
{
	exit(EXIT_FAILURE);
}

int main(int argc, char* argv)
{
	if((0 == argc) && boom())
	{
		fputs("impossible code\n", stderr);
	}
	return 0;
}

** work around code
#include <stdlib.h>
#include <stdio.h>

int boom()
{
	exit(EXIT_FAILURE);
}

int main(int argc, char* argv)
{
	if(0 == argc)
	{
		if(boom())fputs("impossible code\n", stderr);
	}
	return 0;
}