String Macro
2025-12-13
实用小技巧之跨行字符串（字面量）
#define SQL(...) #__VA_ARGS__
const char *foo = SQL(
HELLO WORLD
\n // 111
/* 222 */
next line 111?
""
);
// equal
const char *foo = "HELLO WORLD \n next line 111? \"\"";
细节拆解：
- Stringizing in C involves more than putting double-quote characters around the fragment. 不仅仅会在字符串两端加上双引号
- The preprocessor backslash-escapes the quotes surrounding embedded string constants, and all backslashes within string and character constants. 而且会转义字符串中适当位置的双引号
- Any sequence of whitespace in the middle of the text is converted to a single space in the stringized result. 像 Markdown 一样压缩所有的空白字符到一个空格
- Comments are replaced by whitespace 忽略注释（因为注释会在预处理器之前被处理）
上下文
为了给 bushi-index 找可以学习的素材，在 GitHub 搜索 SQLite3 项目找到了这里。 对 SQL 来说（吃掉换行符）转为一行的行为，比转成多行然后前面带缩进好。不错！