FLEX无法构建lex.yy.c(FLEX Cannot build lex.yy.c)

 
 下载flex-2.5.37.tar.gz 
 
 解压缩并按照INSTALL的说明进行操作： ./configure + make + make install 
 
 在一个新文件夹中，我编写了一个文件example.l其中包含： 
%{
int a = 0, b = 0;
%}

%%
\n   ++a; ++b;
.    ++b;

%%
int main()
{
     yylex();
     printf("%d - %d", a, b);
}
 这是他们网站的一个基本例子。 计算文件中的行和字符。 
 
 在终端中，我运行flex example.l 。 它生成了lex.yy.c 
 
 之后： 
 - gcc lex.yy.c -o lexyy ： 为体系结构x86_64抛出未定义的符号 
 - gcc lex.yy.c -lfl ： ld：找不到-lfl的库 
 - gcc lex.yy.c -ll ：生成a.out ，但是当我针对文件运行它时，它不起作用（打印“0 - 0”）。 

 似乎我无法编译这个该死的文件。 它如何知道在哪里找到必要的库？ 不应该从这里链接工作（这个当前文件夹）？ 
 我无法得到最简单的例子，这有点令人沮丧。 

 
 Downloaded flex-2.5.37.tar.gz 
 
 Unpacked and followed INSTALL's instructions: ./configure + make + make install 
 
 In a new folder, I've written a file example.l containing:
 
%{
int a = 0, b = 0;
%}

%%
\n   ++a; ++b;
.    ++b;

%%
int main()
{
     yylex();
     printf("%d - %d", a, b);
}
 
which is a basic example from their website. Counting lines and characters in a file.
 
 
 In a terminal, I ran flex example.l. It generated lex.yy.c 
 
 After that: 
 - gcc lex.yy.c -o lexyy: Throws undefined symbols for architecture x86_64 
 - gcc lex.yy.c -lfl: ld: library not found for -lfl 
 - gcc lex.yy.c -ll: Generates a.out, but when I run it against a file, it doesn't work (prints "0 - 0"). 
 
 
It seems that I can't get this damn file to compile. How does it know where to find the necessary libraries? Shouldn't the linking work from here (this current folder)? 
 
It's a bit depressing that I can't get the simplest of examples going. 
 

原文：https://stackoverflow.com/questions/21223862