DOS 與 Unix 換行符號的問題

編譯時有時會出現

uncgi.c:52: parse error before `>='
uncgi.c: In function `url_unescape':
uncgi.c:104: stray '\' in program
uncgi.c:104: parse error before `('
uncgi.c:104: parse error before `||'
uncgi.c:104: stray '\' in program
uncgi.c:109: parse error before `else'

而 code 裡看起來感覺卻很正常

#define ishex(x) (((x) >= '0' && (x) <= '9') || ((x) >= 'a' && (x) <= 'f') || \
((x) >= 'A' && (x) <= 'F'))

但如果將句尾的 \ 移除，此部份即可正常編譯

此時可以試試用 flip -ub *.c 或 flip -ub *.h 將換行符號轉為 unix 型式，再編輯看看。
若這樣就可以正常編譯，那麼問題就可以確定是 DOS 及 Unix 所引起的了。
可以參考下面這篇的解釋
http://sources.redhat.com/ml/ecos-discuss/2001-11/msg00064.html
原文節錄如下

li hui  writes:
> I meet a strange problem, when I use '\' in my program
> to indicate a newline, compiler(i386-elf-gcc under
> CYGWIN) promote error that stray '\' in program.
> I was puzzled by this error.

Chances are this is a newlines problem.  Your sources are mounted in text
mode rather than binary mode, or vice versa; I don't understand nasty
windows-isms myself, but I know that can be the source of that problem.

The underlying cause is that you wrote (for example)

#define FRED(x) \
 x++

and you want the compiler to see (as a series of bytes)

......[NL]#define FRED(x) \[NL][TAB]x++[NL]......

(newline then tab between "\" and "x") but it is actually seeing

....[CR][NL]#define FRED(x) \[CR][NL][TAB]x++[CR][NL]......

because the file is being presented with DOS line endings (CR-LF) rather
than just an LF.  And \[CR] is not a continuation symbol to the compiler.

I suspect a more detailed answer will be available in the archives of this
list.

HTH,

 - Huge