Lua1.0 Environment Preparation

Reprint Source: http://my.oschina.net/xhan/blog/306719

Start with the main function of LUA.C and see what happens during the execution of the code.

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if(argc < 2) {  puts("usage: lua filename [functionnames]");  return; }

Lua1.0 must have at least one parameter to execute, or exit directly.
Then there are three lua_register.

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123	lua_register ("callfunc", callfunc); lua_register ("execstr", execstr); lua_register ("test", test);

To see what Lua_register is? You can see that Lua_register is a macro, defined in LUA.H:

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1	#define lua_register(n,f)    (lua_pushcfunction(f), lua_storeglobal(n))

And then look at Lua_pushcfunction, and Lua_storeglobal,
In the opcode.c file

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/*** Push an object (tag=cfunction) to stack. Return 0 on success or 1 on error.*/intlua_pushcfunction (lua_CFunction fn){ if((top-stack) >= MAXSTACK-1) {  lua_error ("stack overflow");  return1; } tag(top) = T_CFUNCTION; fvalue(top++) = fn; return0;}

The lua_pushcfunction parameter is a function pointer, and at the end of the call, the Object type at the top of the stack is set to T_cfunction, and the value of the function pointer passed to the actual parameter fn. The stack here is a link between Lua and C calling, as a method implemented in C code that is converted to an Object of type t_cfunction.
OPCODE.C file

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/*** Store top of the stack at a global variable array field. ** Return 1 on error, 0 on success.*/intlua_storeglobal (char*name){ intn = lua_findsymbol (name); if(n < 0) return1; if(tag(top-1) == T_MARK) return 1; s_object(n) = *(--top); return0;}

TABLE.C file

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/*** Given a name, search it at symbol table and return its index. If not** found, allocate at end of table, checking oveflow and return its index.** On error, return -1.*/intlua_findsymbol (char*s){ inti; for(i=0; i<lua_ntable; i++)  if (streq(s,s_name(i)))   returni; if(lua_ntable >= MAXSYMBOL-1) {  lua_error ("symbol table overflow");  return-1; } s_name(lua_ntable) = strdup(s); if(s_name(lua_ntable) == NULL) {  lua_error ("not enough memory");  return-1; } s_tag(lua_ntable++) = T_NIL;  return(lua_ntable-1);}

The role of Lua_storeglobal is to store global variables in the symbol table. The argument is a string, which is the name of the global variable, Lua_findsymbol finds the string specified by the parameter in the symbol table, returns its index in the symbol table if found, otherwise, creates a new symbol at the end of the table, returning its index in the table.
Symbol table: In the table.c file

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staticSymbol tablebuffer[MAXSYMBOL] = {                                    {"type",{T_CFUNCTION,{lua_type}}},                                    {"tonumber",{T_CFUNCTION,{lua_obj2number}}},                                    {"next",{T_CFUNCTION,{lua_next}}},                                    {"nextvar",{T_CFUNCTION,{lua_nextvar}}},                                    {"print",{T_CFUNCTION,{lua_print}}}                                                 };

Let's look at the definition of the symbol:

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typedefstruct{ char*name; Object object;} Symbol;

It includes the name of a symbol and a corresponding Object type.
Lua_storeglobal after Lua_findsymbol returns, use the returned index to locate the corresponding symbol and set its obejct field. To this, the method registers Lua_register ("Callfunc", Callfunc); The call is complete. So, Lua_register ("Callfunc", Callfunc); is to register a function named "Callfunc" in the global symbol table, and when called in a Lua script, the callfunc is the C function. The other functions are registered with the same.
Registration of the function library:

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123	iolib_open (); strlib_open (); mathlib_open ();

As you can see, the registration of library functions is also using the Lua_register macro mentioned above. After the call is complete, all of the system's own functions have been registered.
Here, the environment is ready to start working:

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1	lua_dofile (argv[1]);

The following code handles the arguments that start with the second argument of the command line as an parameterless function call.

Lua1.0 Environment Preparation