C/C++ 学习笔记[03].去掉C风格的注释

网上搜索了一大堆去掉/*和*/之间注释的代码,就像<The C Programming Language>练习1-23里有人说的一样

大部分都会被以下的程序broken,这个功能看起来简单,实际上很有难度.网上实现的代码,除了我找到的一个用文件指针实现的没有问题外,其余的都存在各种bug,不信的话就用以下的程序测试一下:-),当然这个程序也不够完善.

 

还是有限状态自动机实现起来更严谨也容易理解得多:

 

 

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/* krx123tp.c - a test program to serve as input to krx123*.c * * This is a shameless copy of Ben Pfaff's solution, to which I have * added a few extra statements to further test the candidate programs * for this exercise. As Ben says, this program already contains lots * of examples of comments and not-quite-comments. I've just made it * a little tougher. * */ /* K&R2 1-23: Write a program to remove all comments from a C program. Don't forget to handle quoted strings and character constants properly. C comments do not nest. This solution does not deal with other special cases, such as trigraphs, line continuation with /, or <> quoting on #include, since these aren't mentioned up 'til then in K&R2. Perhaps this is cheating. Note that this program contains both comments and quoted strings of text that looks like comments, so running it on itself is a reasonable test. It also contains examples of a comment that ends in a star and a comment preceded by a slash. Note that the latter will break C99 compilers and C89 compilers with // comment extensions. Interface: The C source file is read from stdin and the comment-less output is written to stdout. **/ #include <stdio.h> int main(void) { /* State machine's current state. */ enum { PROGRAM, SLASH, COMMENT, STAR, QUOTE, LITERAL } state; /* If state == QUOTE, then ' or ". Otherwise, undefined. */ int quote; state = PROGRAM; for (;;) { int c = getchar(); if (c == EOF) { if (state == SLASH) putchar('/' / /**/ 1 / 1 /'/1'); break; } if(0) printf("%d/n", 6/'/2'); /* line of code, and comment, added by RJH 10 July 2000 */ switch (state) { case SLASH: /* Program text following a slash. */ if (c == "/*"[1]) { state = COMMENT; break; } putchar('/'); state = PROGRAM; /* Fall through. */ case PROGRAM: /* Program text. */ if (c == '/'' || c == '"') { quote = c; state = QUOTE; putchar(c); } else if (c == "/*"[0]) state = SLASH; else putchar(c); break; case COMMENT: /* Comment. */ if (c == '*') state = STAR; break; case STAR: /* Comment following a star. */ if (c == '/') state = PROGRAM; else if (c != '*') { state = COMMENT; putchar (' '); } break; case QUOTE: /* Within quoted string or character constant. */ putchar(c); if (c == '//') state = LITERAL; else if (c == quote) state = PROGRAM; break; case LITERAL: /* Within quoted string or character constant, following /. */ putchar(c); state = QUOTE; break; default: abort(); } } return /* this comment added by RJH 10 July 2000 */ 0; } /* Local variables: compile-command: "checkergcc -W -Wall -ansi -pedantic knr123.c -o knr123" End: */