gcc会在转换单元为空时报告一个诊断，这是C标准所要求的。要使gcc满意，可以在空的.c文件中添加一个...
ANSI/ISO C Specification Language CAT RNTL project 2.3 Function contracts tset ::= \empty empty set | term singleton | tset -> id | tset . id | * tset | tset [ tset ] | term? .. term? range | \union ( tset (, tset)∗ ) union of locations | \inter ( tset (, tset)∗...