linking error

[sana24]

Hello all,
I use microsoft visual studio 6.0 and i have this error when I try to built my application :

vhdl.obj : error LNK2001: unresolved external symbol _yylex
LIBCD.lib(wincr t0.obj) : error LNK2001: unresolved external symbol _WinMain@16
Debug/parseur_vhdl.ex e : fatal error LNK1120: 2 unresolved externals
Error executing link.exe.
parseur_vhdl.ex e - 3 error(s), 0 warning(s)

Any help please!!

[tyreld]

Its hard to say for sure since you haven't supplied any of your code for us to look at. However, my first guess is that you aren't linking all the necessary object files (ie. the linker can't find the following functions "yylex()" and "WinMain()" ).

[sana24]

Its hard to say for sure since you haven't supplied any of your code for us to look at. However, my first guess is that you aren't linking all the necessary object files (ie. the linker can't find the following functions "yylex()" and "WinMain()" ).

vhdl.o is from vhdl.c, this file is generated by bison. My application is a vhdl parser.

[tyreld]

vhdl.o is from vhdl.c, this file is generated by bison. My application is a vhdl parser.

Okay, the problem is that bison only generates the necessary code for parsing some set of tokens. The parsing code expects a function yylex for obtaining tokens. Generally, your lexer code would be generated by flex or lex. Finally neither one of these code generators produces a main method. You need to supply the rest of this code to produce a working application.

[sana24]

Okay, the problem is that bison only generates the necessary code for parsing some set of tokens. The parsing code expects a function yylex for obtaining tokens. Generally, your lexer code would be generated by flex or lex. Finally neither one of these code generators produces a main method. You need to supply the rest of this code to produce a working application.

In addition, i have a main.c which is an application using this parser

[tyreld]

In addition, i have a main.c which is an application using this parser

It would seem that main.o isn't being supplied to the linker at link time then.

[sana24]

It would seem that main.o isn't being supplied to the linker at link time then.

I check it main.o is supplied to the linker

[Banfa]

You have compiler/linker options set that tell the compiler/linker that it is linking a Windows program and to look for WinMain as the entry point instead of main.

However you have supplied a main (because it is a console application?).

Check your linker options (and then your compiler options).

[sana24]

You have compiler/linker options set that tell the compiler/linker that it is linking a Windows program and to look for WinMain as the entry point instead of main.

However you have supplied a main (because it is a console application?).

Check your linker options (and then your compiler options).

I changed the type of my projetc win32 application to win32 consol application.
I have now one error just:
vhdl.obj : error LNK2001: unresolved external symbol _yylex

[Banfa]

I changed the type of my projetc win32 application to win32 consol application.
I have now one error just:
vhdl.obj : error LNK2001: unresolved external symbol _yylex

which tyreId has already addressed in this post.

basically it can't locate it because you haven't written it.

[sana24]

which tyreId has already addressed in this post.

basically it can't locate it because you haven't written it.

i don't understand you?what is the problem?

[Banfa]

Have you written a function called yylex?

[sana24]

Have you written a function called yylex?

NO, but In the code there is
extern "C"
{int yylex(void);}

[tyreld]

i don't understand you?what is the problem?

A parser is made up of two parts, a lexical analyzer and a syntactic/semantic analyzer. Although, problematically the term "parser" is often used to describe both the syntatctic/semantic analyzer as well as the combination of both the lexical and syntactic/semantic analyzers.

1.) Lexical analysis breaks the source language text into small pieces called tokens. Each token is a single atomic unit of the language, for instance a keyword, identifier or symbol name. The token syntax is typically a regular language, so a finite state automaton constructed from a regular expression can be used to recognize it. This phase is also called lexing or scanning, and the software doing lexical analysis is called a lexical analyzer or scanner.

2.) Syntax analysis involves parsing the token sequence to identify the syntactic structure of the program.

3.) Semantic analysis is the phase that checks the meaning of the program to ensure it obeys the rules of the language. One example is type checking. A parser emits most diagnostics during semantic analysis, and frequently combines it with syntax analysis.

Bison is a parser generator. However, it only generates code that deals with the phases described in item 2 and item 3. What this means is that the code generated by Bison requires a seperate implementation of the lexical phase described in item 1.

Bison provides a function called yyparse that is the entry point into the parser. However, yyparse expects a function called yylex to be defined to generate tokens from the source language. You either have to write this function yourself, or use a lexical analyzer generator tool like flex to generate it for you.

The following page provides some good resources on building parsers/compilers using Lex/Yacc or the modern GNU equivalents Flex/Bison.

The Lex and Yacc Page

[tyreld]

NO, but In the code there is
extern "C"
{int yylex(void);}

That is simply telling the compiler that a function "yylex" is declared in a seperate source file, and that it should not treat the non-existance of that function in source file being compiled as an error. This is necessary because as I described before Bison generates a function yyparse that is dependent on the existance of a function yylex to function properly.