error: implicit declaration of function ‘VerifyFixClassname‘ is invalid in C99 [-Werror,-Wimplicit-f

具体错误：

/Users/tsit/tsjdk8-project/openjdk8/jdk/src/share/native/sun/misc/URLClassPath.c:58:5: error: implicit declaration of function 'VerifyFixClassname' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    VerifyFixClassname(clname);
    ^
/Users/tsit/tsjdk8-project/openjdk8/jdk/src/share/native/sun/misc/URLClassPath.c:60:10: error: implicit declaration of function 'VerifyClassname' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    if (!VerifyClassname(clname, JNI_TRUE)) {  /* expects slashed name */
         ^
/Users/tsit/tsjdk8-project/openjdk8/jdk/src/share/native/sun/misc/URLClassPath.c:60:10: note: did you mean 'VerifyFixClassname'?
/Users/tsit/tsjdk8-project/openjdk8/jdk/src/share/native/sun/misc/URLClassPath.c:58:5: note: 'VerifyFixClassname' declared here
    VerifyFixClassname(clname);
    ^
2 errors generated.      

解决办法：

原因就是没有include头文件。最简单办法就是来个外部声明：

extern jboolean VerifyFixClassname(char* name);
extern jboolean VerifyClassname(char* name, jboolean allowArrayClass);      

如果找到了头文件，直接包含对应的头文件最好。