多年沒用C語言了。近日用R語言編程時因有太多循環，只好用C寫個擴展模塊，一時竟不知怎么動手了。在多種語言中，單引號和雙引號是可以等同使用的。因鍵入雙引號要比單引號多按一SHIFT鍵，我偏好單引號。在用printf顯示字符串， 我就自然地用上了單引號來定義格式串，哪知用gcc編譯時竟出錯了：

[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]$

改回雙引號后，才順利編譯。

實在不記得C語言中單雙引號的區別了，不知是當初沒學好，還是搞忘了，抑或是gcc的一個特點？