多年没用C语言了。近日用R语言编程时因有太多循环，只好用C写个扩展模块，一时竟不知怎么动手了。在多种语言中，单引号和双引号是可以等同使用的。因键入双引号要比单引号多按一SHIFT键，我偏好单引号。在用printf显示字符串， 我就自然地用上了单引号来定义格式串，哪知用gcc编译时竟出错了：

[xxia@xxq 4Mike]$ gcc pvc.c

pvc.c:179:9: warning: multi-character character constant

pvc.c: In function ‘pv_concord_more’:

pvc.c:179: warning: passing argument 1 of ‘printf’ makes pointer from integer without a cast

pvc.c:184:9: warning: multi-character character constant

pvc.c:184: warning: passing argument 1 of ‘printf’ makes pointer from integer without a cast

pvc.c:229:9: warning: multi-character character constant

pvc.c:229: warning: passing argument 1 of ‘printf’ makes pointer from integer without a cast

pvc.c:232:9: warning: multi-character character constant

pvc.c:232: warning: passing argument 1 of ‘printf’ makes pointer from integer without a cast

[xxia@xxq 4Mike]$

改回双引号后，才顺利编译。

实在不记得C语言中单双引号的区别了，不知是当初没学好，还是搞忘了，抑或是gcc的一个特点？