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 Post subject: gcc -D變數
PostPosted: Fri Mar 01, 2013 3:54 pm 
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Joined: Fri Mar 04, 2011 9:36 pm
Posts: 500
舉個例子:
nds32le-elf-gcc -O3 -c -DUSR_ENTRY=0x80000 ...(後面不重要,省略)

類似於#define。
在main.c裡有一個 user_pc = (unsigned long)USR_ENTRY;
我們將這個變數的define寫在makefile裡。

下面是gcc對-D的說明。
-D name=definition
The contents of definition are tokenized and processed as if they appeared during
translation phase three in a ‘#define’ directive. In particular, the definition
will be truncated by embedded newline characters.
If you are invoking the preprocessor from a shell or shell-like program you may
need to use the shell’s quoting syntax to protect characters such as spaces that
have a meaning in the shell syntax.
If you wish to define a function-like macro on the command line, write its
argument list with surrounding parentheses before the equals sign (if any).
Parentheses are meaningful to most shells, so you will need to quote the option.
With sh and csh, ‘-D’name(args...)=definition’’ works.
‘-D’ and ‘-U’ options are processed in the order they are given on the command
line. All ‘-imacros file’ and ‘-include file’ options are processed after all
‘-D’ and ‘-U’ options.


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