为什么程序没有运行flex和bison编译的C程序的主要功能

I've written a bison parser using flex and c. The parser is compiled without error, but when I run the executable file the main function is not executed (It doesn't print out the first line after the main declaration that is actually a print instruction)

我用flex和c编写了一个野牛解析器。解析器编译时没有错误，但是当我运行可执行文件时，不执行main函数（它不会在主声明之后打印出第一行，实际上是打印指令）

main( int argc, char *argv[] )
{
  printf("*** C2P version 1.0 @2015***\n");
  extern FILE *yyin;
  ++argv; --argc;
  printf("Open C file %s...",argv[0]);
  yyin = fopen( argv[0], "r" );
  if (yyin==NULL) {
  printf("ERROR file not found %s", argv[0]);
  exit(1);
}
  yydebug = 1; //enable debug
  yyparse();
  exit(0);
}

I've used the following commands for compiling:

我使用以下命令进行编译：

bison -d c_def.y
flex c_def.l
gcc c_def.tab.h lex.yy.c -o c2p -lfl

1 个解决方案

#1

This is wrong:

这是错的：

gcc c_def.tab.h lex.yy.c -o c2p -lfl

The bison parser is in the file c_def.tab.c. c_def.tab.h is just the header file containing the token definitions.

野牛解析器位于文件c_def.tab.c中。 c_def.tab.h只是包含令牌定义的头文件。

So there wouldn't be a main() at all in c2p if it were not for your inclusion of the flex library (-lfl). That library includes a main function which calls the lexer until it returns an end-of-file indicator. (It does not call the parser, which is why your parser is not being called.)

因此，如果不包含flex库（-lfl），则c2p中根本不会有main（）。该库包含一个main函数，它调用词法分析器直到它返回文件结束指示符。（它不会调用解析器，这就是为什么不调用解析器的原因。）

You probably shouldn't use -lfl. Aside from the main() function which you don't need, the only other thing it contains is a fake implementation of yywrap which always returns 1; instead of relying on that, just include the option

你可能不应该使用-lfl。除了你不需要的main（）函数之外，它包含的唯一另一个东西是yywrap的伪实现，它总是返回1;而不是依赖于它，只需包括选项

%option noyywrap

in your flex definition, and then your lexer won't depend on yywrap at all.

在你的flex定义中，然后你的词法分析器根本不依赖于yywrap。

#1