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

具體錯誤：

/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.      

解決辦法：

原因就是沒有include頭檔案。最簡單辦法就是來個外部聲明：

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

如果找到了頭檔案，直接包含對應的頭檔案最好。