Quine in C: a self-printing program

Quine's are sometimes assigned as homework problems in classes such as Theory of Computation for the instructor's amusement and, suprisingly, also the students'.

You can find out more about the logic behind quines by reading and understanding the Recursion Theorem in computability. See Prof. Michael Sipser's book Introduction to the Theory of Computation, 3rd ed., at page 245, for a very nice explanation.

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Source code below

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char * unescapeStr(char * s);

char tape[65536];

void b(void)
{
	printf("%s\n\nint main(int argc, char ** argv)\n{\n\tstrcpy(tape, \"%s\");\n\tb();\n\treturn 0;\n}\n\nchar * unescapeStr(char * s)\n{\n\tint l = strlen(s);\n\tchar * n = malloc(l * 2 + 1);\n\tchar * p = n;\n\tfor(int i = 0; i < l; i++) {\n\t\tswitch(s[i])\n\t\t{\n\t\t\tcase '\\n':\n\t\t\t\t*p++ = '\\\\';\n\t\t\t\t*p++ = 'n';\n\t\t\t\tbreak;\n\t\t\tcase '\\t':\n\t\t\t\t*p++ = '\\\\';\n\t\t\t\t*p++ = 't';\n\t\t\t\tbreak;\n\t\t\tcase '\\\\':\n\t\t\t\t*p++ = '\\\\';\n\t\t\t\t*p++ = '\\\\';\n\t\t\t\tbreak;\n\t\t\tcase '\\\"':\n\t\t\t\t*p++ = '\\\\';\n\t\t\t\t*p++ = '\\\"';\n\t\t\t\tbreak;\n\t\t\tdefault:\n\t\t\t\t*p++ = s[i];\n\t\t\t\tbreak;\n\t\t}\n\t\t*p = 0;\n\t}\n\n\treturn n;\n}\n", tape, unescapeStr(tape));
}

int main(int argc, char ** argv)
{
	strcpy(tape, "#include <stdio.h>\n#include <string.h>\n#include <stdlib.h>\n\nchar * unescapeStr(char * s);\n\nchar tape[65536];\n\nvoid b(void)\n{\n\tprintf(\"%s\\n\\nint main(int argc, char ** argv)\\n{\\n\\tstrcpy(tape, \\\"%s\\\");\\n\\tb();\\n\\treturn 0;\\n}\\n\\nchar * unescapeStr(char * s)\\n{\\n\\tint l = strlen(s);\\n\\tchar * n = malloc(l * 2 + 1);\\n\\tchar * p = n;\\n\\tfor(int i = 0; i < l; i++) {\\n\\t\\tswitch(s[i])\\n\\t\\t{\\n\\t\\t\\tcase '\\\\n':\\n\\t\\t\\t\\t*p++ = '\\\\\\\\';\\n\\t\\t\\t\\t*p++ = 'n';\\n\\t\\t\\t\\tbreak;\\n\\t\\t\\tcase '\\\\t':\\n\\t\\t\\t\\t*p++ = '\\\\\\\\';\\n\\t\\t\\t\\t*p++ = 't';\\n\\t\\t\\t\\tbreak;\\n\\t\\t\\tcase '\\\\\\\\':\\n\\t\\t\\t\\t*p++ = '\\\\\\\\';\\n\\t\\t\\t\\t*p++ = '\\\\\\\\';\\n\\t\\t\\t\\tbreak;\\n\\t\\t\\tcase '\\\\\\\"':\\n\\t\\t\\t\\t*p++ = '\\\\\\\\';\\n\\t\\t\\t\\t*p++ = '\\\\\\\"';\\n\\t\\t\\t\\tbreak;\\n\\t\\t\\tdefault:\\n\\t\\t\\t\\t*p++ = s[i];\\n\\t\\t\\t\\tbreak;\\n\\t\\t}\\n\\t\\t*p = 0;\\n\\t}\\n\\n\\treturn n;\\n}\\n\", tape, unescapeStr(tape));\n}");
	b();
	return 0;
}

char * unescapeStr(char * s)
{
	int l = strlen(s);
	char * n = malloc(l * 2 + 1);
	char * p = n;
	for(int i = 0; i < l; i++) {
		switch(s[i])
		{
			case '\n':
				*p++ = '\\';
				*p++ = 'n';
				break;
			case '\t':
				*p++ = '\\';
				*p++ = 't';
				break;
			case '\\':
				*p++ = '\\';
				*p++ = '\\';
				break;
			case '\"':
				*p++ = '\\';
				*p++ = '\"';
				break;
			default:
				*p++ = s[i];
				break;
		}
		*p = 0;
	}

	return n;
}