42/42_EXT_01_dr_quine
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42_EXT_01_dr_quine/notes.md
Hugo LAMY 15beb4aa3f fix mismatch xstr vs str
2025-01-04 11:30:57 +01:00

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- [interactions between MACRO and comments](https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html#:~:text=the%20stringized%20result.-,Comments,-are%20replaced%20by)
- [preprocessor strip comments before exapnding macros](https://stackoverflow.com/questions/1510869/does-the-c-preprocessor-strip-comments-or-expand-macros-first)
- [create an include with a macro OR NOT](https://stackoverflow.com/questions/1135822/escaping-a-symbol-in-a-define-macro)
---
## make rules :
- make in root will make all projects
- make in each project will compile this project
- make diff : compile if necessary, and run the program then compare the output
- make concat : create the concatenated version, finale version, of the quine
## folder structure
> Each programs will have to be coded in C and in Assembly, and respectivly in a folder named C and ASM, each folders containing its own Makefile with the usual rules.
```
dr_quine/
| C/
| | Colleen.c
| | Grace.c
| | Sully.c
| | Makefile
| | ...
| ASM/
| | Colleen.asm
| | Grace.asm
| | Sully.asm
| | Makefile
| | ...
```
---
## Grace
---
#### 1 : a string containing itself, almost
---
```
#define xstr(s) str(s)
#define str(s) char *quine = #s ; printf(quine);
xstr(str())
```
**expansions :**
-> `xstr ( char *quine = "" ; printf(quine); )`
-> `char *quine = "char *quine = \"\" ; printf(quine);" ; printf(quine);`
**problem :** `\"\"` instead of `#s` :
-> `char *quine = "char *quine = #s ; printf(quine);" ; printf(quine);`
#### 1.2 : the output, first try
---
```
#include <stdio.h>
#define MAIN(s) int main(){ s return 0; }
#define xstr(s) str(s)
#define str(s) char *quine = #s ; printf(quine);
MAIN(xstr(str()))
```
**expansions :**
-> `MAIN( xstr( char *quine = "" ; printf(quine); ))`
-> `MAIN( char *quine = "char *quine = \"\" ; printf(quine);" ; printf(quine); )`
-> `int main(){ char *quine = "char *quine = \"\" ; printf(quine);" ; printf(quine); return 0; }`
**exploded view :**
```
int main(){
char *quine = "char *quine = \"\" ; printf(quine);" ;
printf(quine);
return 0;
}
```
**output :**
```
char *quine = "" ; printf(quine);
```
**problem 1 :** missing the main function around the content
**problem 2 :** quine does not contain itself, but an empty string
#### 1.3 : the output, second try
---
```
#include <stdio.h>
#define MAIN(s) int main(){ s return 0; }
#define xstr(s) str(s)
#define str(s) char *quine = #s ; printf(quine);
MAIN(xstr(MAIN(xstr(str()))))
```
**expansions :**
-> `MAIN( xstr( MAIN( xstr( char *quine = "" ; printf(quine); ))))`
-> `MAIN( xstr( MAIN( char *quine = "char *quine = \"\" ; printf(quine);" ; printf(quine); )))`
-> `MAIN( xstr( int main(){ char *quine = "char *quine = \"\" ; printf(quine);" ; printf(quine); return 0; } ))`
-> `MAIN( char *quine = "int main(){ char *quine = \"char *quine = \\\"\\\" ; printf(quine);\" ; printf(quine); return 0; }" ; printf(quine); )`
-> `int main(){ char *quine = "int main(){ char *quine = \"char *quine = \\\"\\\" ; printf(quine);\" ; printf(quine); return 0; }" ; printf(quine); return 0; }`
**exploded view :**
```
int main()
{
char *quine =
"
int main()
{
char *quine = \"char *quine = \\\"\\\" ; printf(quine);\" ;
printf(quine);
return 0;
}
";
printf(quine);
return 0;
}
```
**output :**
```
int main(){ char *quine = "char *quine = \"\" ; printf(quine);" ; printf(quine); return 0; }%
```
**exploded view :**
```
int main()
{
char *quine = "char *quine = \"\" ; printf(quine);";
printf(quine);
return 0;
}
```
**problem :** this new program will only print :
`char *quine = "" ; printf(quine);`
#### 1.3 : the output, third try
---
```
#include <stdio.h>
#define MAIN(s) int main(){ s return 0; }
#define xstr(s) str(s)
#define str(s) char *quine = #s ; printf(quine);
MAIN(xstr(MAIN(xstr(MAIN(xstr())))))
```
**output :**
`int main(){ char *quine = "int main(){ char *quine = \"\" ; printf(quine); return 0; }" ; printf(quine); return 0; }`
**exploded view :**
```
int main()
{
char *quine =
"
int main()
{
char *quine = \"\";
printf(quine);
return 0;
}
";
printf(quine);
return 0;
}
```
**problem :** we cannot gon on like this, there will always be one level missing
**idea :** changing the inner `char* quine =` content to '%s' and printing `printf(quine, quine)`
#### 2 : second approach
---
**a quine could be this structure basically :**
```
int main()
{
char *quine = THE_WHOLE_PROGRAM;
printf(quine);
return 0;
}
```
**with macros :**
```
#include <stdio.h>
#define MAIN() int main() { char *quine = "BEFORE" "THIS_MACRO_ITSELF" "AFTER"; printf(quine); return 0; }
MAIN()
```
#### 2.1 : let's try it
---
```
#include <stdio.h>
#define MAIN(s) \
int main() \
{ \
char *quine = "#include <stdio.h>\n#define MAIN(s) " \
s \
"\n\nMAIN(s)\n"; \
printf(quine); \
return 0; \
}
MAIN(s)
```
**expands to :**
```
int main()
{
char *quine = "#include <stdio.h>\n#define MAIN(s) "
s
"\n\nMAIN(s)\n";
printf(quine);
return 0;
}
```
**problem :** the `char *quine` string should contain a copy of the whole code in place of "s"
#### 2.2 : second try, macro calling itself : MAIN(MAIN)
---
```
#include <stdio.h>
#define MAIN(s) \
int main() \
{ \
char *quine = "#include <stdio.h>\n#define MAIN(s) " \
s \
"\n\nMAIN(MAIN(s))\n"; \
printf(quine); \
return 0; \
}
MAIN(MAIN(s))
```
**expands to :**
```
int main()
{
char *quine = "#include <stdio.h>\n#define MAIN(s) " int main()
{
char *quine = "#include <stdio.h>\n#define MAIN(s) "
s
"\n\nMAIN(MAIN(s))\n";
printf(quine);
return 0;
}
"\n\nMAIN(MAIN(s))\n";
printf(quine);
return 0;
}
```
**problem :** almost there, but the content of the string quine should be a litteral string instead of code
#### 2.3 : lets stringify the content of the inner MAIN
---
**the previous can be written with an extra step :**
```
#define str(s) s
#define MAIN(s) content s content
MAIN(str(MAIN(s)))
/* EQUIVALENT TO : */
#define MAIN(s) content s content
MAIN((MAIN(s)))
```
**we can use this extra step to stringify the content with #s :**
```
#define str(s) #s
#define MAIN(s) content s content
MAIN(str(MAIN(s)))
```
**example :**
```
#include <stdio.h>
#define str(s) #s
#define MAIN(s) \
int main() \
{ \
char *quine = "#include <stdio.h>\n#define str(s) #s\n#define MAIN(s) " \
s \
"\n\nMAIN(str(MAIN(s)))\n"; \
printf(quine); \
return 0; \
}
MAIN(str(MAIN(s)))
```
**expands to :**
```
int main()
{
char *quine = "#include <stdio.h>\n#define str(s) #s\n#define MAIN(s) "
"MAIN(s)"
"\n\nMAIN(str(MAIN(s)))\n";
printf(quine);
return 0;
}
```
**problem :** oops, it stringified the parameter name, not it's expanded version, see https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html
#### 2.4 : working stringification
---
```
#include <stdio.h>
#define str(s) #s
#define xstr(s) str(s)
#define MAIN(s) \
int main() \
{ \
char *quine = "#include <stdio.h>\n#define str(s) #s\n#define xstr(s) str(s)\n#define MAIN(s) " \
s \
"\n\nMAIN(xstr(MAIN(s)))\n"; \
printf(quine); \
return 0; \
}
MAIN(xstr(MAIN(s)))
```
**expands to :**
```
int main()
{
char *quine = "#include <stdio.h>\n#define str(s) #s\n#define xstr(s) str(s)\n#define MAIN(s) "
"int main() { char *quine = \"#include <stdio.h>\\n#define str(s) #s\\n#define xstr(s) str(s)\\n#define MAIN(s) \" s \"\\n\\nMAIN(xstr(MAIN(s)))\\n\"; printf(quine); return 0; }"
"\n\nMAIN(xstr(MAIN(s)))\n";
printf(quine);
return 0;
}
```
**output :**
```
#include <stdio.h>
#define str(s) #s
#define xstr(s) str(s)
#define MAIN(s) int main() { char *quine = "#include <stdio.h>\n#define str(s) #s\n#define xstr(s) str(s)\n#define MAIN(s) "s"\n\nMAIN(xstr(MAIN(s)))\n"; printf(quine); return 0; }
MAIN(xstr(MAIN(s)))
```
**victory ;)**
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