[SOLVED] Objects and assignment in interpreter

dwhitney67 · 02-18-2011, 02:05 PM

One way to fix your code is to define function_t as such:

Code:

typedef struct function_t { function_TEMPLATE } function_t;

But I must ask... why in hell are you intentionally obfuscating the readability of the code with macro definitions? From a professional standpoint, it looks like crap. Don't get offended! It is merely my opinion, for which I am entitled to possess.

MTK358 · 02-18-2011, 02:11 PM

Quote:

Originally Posted by dwhitney67

One way to fix your code is to define function_t as such:

Code:

typedef struct function_t { function_TEMPLATE } function_t;

Why is function_t mentioned twice? I don't want to make an instance of function_t, if that's what it does.

Quote:

Originally Posted by dwhitney67

But I must ask... why in hell are you intentionally obfuscating the readability of the code with macro definitions? From a professional standpoint, it looks like crap. Don't get offended! It is merely my opinion, for which I am entitled to possess.

That's the best way I know of to achieve polymorphism in C. The idea is that all the contents of object_t are at the beginning of function_t, that way you can have an object_t pointer and treat it like an object_t, even if it's actually pointing to a function_t.

MTK358 · 02-19-2011, 08:41 AM

I changed it like this:

Code:

#define function_TEMPLATE \
    object_TEMPLATE \
    array_t *param_names; \
    env_t *env; \
    object_t* (*call)(function_t*, array_t*);
struct function { function_TEMPLATE };
typedef struct function function_t;

It still doesn't work.

EDIT:

This is what it looks like after being run through the preprocessor:

Code:

struct function { object_type_t objtype; array_t *param_names; env_t *env; object_t* (*call)(function_t*, array_t*); };
typedef struct function function_t;

I see nothing wrong with it.

ntubski · 02-19-2011, 02:02 PM

You need to put the typedef for function_t before it's first use:

Code:

typedef struct function function_t; /* this goes first! */
#define function_TEMPLATE \
    object_TEMPLATE \
    array_t *param_names; \
    env_t *env; \
    object_t* (*call)(function_t*, array_t*);
struct function { function_TEMPLATE };

MTK358 · 02-19-2011, 03:07 PM

That fixed that issue. I didn't notice that the definition for function_t included function_t.

But now there's another one:

Code:

node_function.h:11:5: error: expected specifier-qualifier-list before ‘node_t’
node_function.h:14:70: error: expected declaration specifiers or ‘...’ before ‘node_t’

Code:

#ifndef __NODE_FUNCTION_H_INCLUDE_GUARD
#define __NODE_FUNCTION_H_INCLUDE_GUARD

#include "function.h"
#include "object.h"
#include "ast.h"

typedef struct node_function node_function_t;
struct node_function {
    function_TEMPLATE
    node_t *node;
};

node_function_t* node_function_new(array_t *param_names, env_t *env, node_t *node);

#endif

This can't have te same problem because the definition does not include node_function_t. And what's a "specifier-qualifier-list"?

ntubski · 02-19-2011, 05:23 PM

Where is the declaration for node_t?

MTK358 · 02-19-2011, 05:38 PM

In ast.h.

ntubski · 02-19-2011, 06:22 PM

The error message suggests that the declaration for node_t is missing, it's impossible to say more without seeing the rest of the code.

MTK358 · 02-19-2011, 07:01 PM

ast.h:

Code:

#ifndef __AST_H_INCLUDE_GUARD__
#define __AST_H_INCLUDE_GUARD__

#include "object.h"
#include "env.h"

#include "number_type.h"
#include "string_type.h"
#include "boolean_type.h"
#include "c_function.h"
#include "node_function.h"

#include <setjmp.h>
#include <stdarg.h>

typedef enum {
    NODETYPE_NUMBER,   
    //NODETYPE_FLOAT,     
    NODETYPE_STRING,    // create String
    NODETYPE_IF,        // evaluate only if condition true/false
    NODETYPE_WHILE,     // loop while condition true
    NODETYPE_DOWHILE,   // loop while condition true, eval body at least once
    NODETYPE_CALL,      // call function
    NODETYPE_MEMBER, // get member from env ('.' operator)
    NODETYPE_ASSIGN,    // assign value to lvalue ('=' operator)
    NODETYPE_FUNC,      // create anonymous function
    NODETYPE_THIS,
    NODETYPE_THROW,
    NODETYPE_TRY,
	NODETYPE_INSIDE,
	NODETYPE_BOOLEAN,
	NODETYPE_BLOCK,
	NODETYPE_SCOPE,
} nodetype_t;

typedef struct node node_t;
struct node {
    nodetype_t type;
    int child_count;
    node_t **children;
    void *payload;
};

extern jmpbuf_t exception_jmpbuf;
extern object_t *exception_object;

node_t* node_new(nodetype_t type, char *payload, int child_count, ...);

object_t *create_exception_env(object_t *name, object_t *message);

void node_eval_throw_exception(object_t *e);

object_t* node_eval(node_t *node, env_t *env);

#endif

ntubski · 02-19-2011, 07:33 PM

I can't reproduce the error with the bits you've posted so far. I did notice that you have jmpbuf_t instead of jmp_buf.

MTK358 · 02-20-2011, 09:41 AM

Code:

ast.c:143:30: error: incompatible types when assigning to type ‘jmp_buf’ from type ‘struct __jmp_buf_tag *’
ast.c:145:30: error: incompatible types when assigning to type ‘jmp_buf’ from type ‘struct __jmp_buf_tag *’

What does this mean? I read about it and heard that jmp_buf is actually an array, but why doesn't this work?

Sergei Steshenko · 02-20-2011, 02:22 PM

Quote:

Originally Posted by MTK358

Code:

ast.c:143:30: error: incompatible types when assigning to type ‘jmp_buf’ from type ‘struct __jmp_buf_tag *’
ast.c:145:30: error: incompatible types when assigning to type ‘jmp_buf’ from type ‘struct __jmp_buf_tag *’

What does this mean? I read about it and heard that jmp_buf is actually an array, but why doesn't this work?

Copy-paste your code, including declaration of 'jmp_buf' and of '__jmp_buf_tag'.

What are you trying to do ? To assign to the whole array and not to array element ?

MTK358 · 02-20-2011, 02:35 PM

I never mentioned "__jmp_buf_tag" anywhere in my code. All I'm doing is assigning a variable to another, both of type "jmp_buf".

Code:

extern jmp_buf exception_jmpbuf;                                      ast.h, line 44
extern object_t *exception_object;

-----

#include "ast.h"                                                      ast.c, line 1

jmp_buf exception_jmpbuf;
object_t *exception_object;

<snip>

    else if (type == NODETYPE_THROW)                                  line 133
    {
        node_eval_throw_exception(node_eval(node->children[0], env));
		
    }
    else if (type == NODETYPE_TRY)
    {
        jmp_buf prev_jmpbuf = exception_jmpbuf;
        if (setjmp(exception_jmpbuf) == 0) {
            node_eval(node->children[0], env);
            exception_jmpbuf = prev_jmpbuf;                           line 143
        } else {
            exception_jmpbuf = prev_jmpbuf;                           line 145
            env_set(env, "exception", exception_object);
            node_eval(node->children[1], env);
            env_del(env, "exception");
            exception_object = NULL;
        }
        return NULL;
    }

Sergei Steshenko · 02-20-2011, 03:43 PM

Quote:

Originally Posted by MTK358

I never mentioned "__jmp_buf_tag" anywhere in my code. ...

Then probably it's a result of some macro substitution. You need to look at preprocessed code (gcc -E ....).

MTK358 · 02-20-2011, 04:14 PM

it still says "jmp_buf" everywhere.

I think I heard that jmp_buf is a typedef to an array or something?