java 错误：“->”的基操作数具有非指针类型“JNIEnv”
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error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
提问by Rorschach
#include <stdio.h>
#include <jni.h>
JNIEnv* create_vm() {
JavaVM* jvm;
JNIEnv* env;
JavaVMInitArgs args;
JavaVMOption options[1];
/* There is a new JNI_VERSION_1_4, but it doesn't add anything for the purposes of our example. */
args.version = JNI_VERSION_1_2;
args.nOptions = 1;
options[0].optionString = "-Djava.class.path=/home/test/workspace/pankajs/"
"jikes/JikesRVMia32-linuxproduction/target/tests/stress/prototype/basic/classes";
args.options = options;
args.ignoreUnrecognized = JNI_FALSE;
JNI_CreateJavaVM(&jvm, (void **)&env, &args);
return env;
}
void invoke_class(JNIEnv* env) {
jclass helloWorldClass;
jmethodID mainMethod;
jobjectArray applicationArgs;
jstring applicationArg0;
helloWorldClass = (*env)->FindClass(env, "/test/org/jikesrvm/basic/core/bytecode/TestSwitch");
mainMethod = (*env)->GetStaticMethodID(env, helloWorldClass, "main", "([Ljava/lang/String;)V");
applicationArgs = (*env)->NewObjectArray(env, 1, (*env)->FindClass(env, "java/lang/String"), NULL);
applicationArg0 = (*env)->NewStringUTF(env, "From-C-program");
(*env)->SetObjectArrayElement(env, applicationArgs, 0, applicationArg0);
(*env)->CallStaticVoidMethod(env, helloWorldClass, mainMethod, applicationArgs);
}
int main(int argc, char **argv) {
JNIEnv* env = create_vm();
invoke_class( env );
}
I am trying to learn how JVM is actually invoked from bootstrap C files.
I found this example on internet and I am facing some problems while running it.
我在互联网上找到了这个例子，我在运行它时遇到了一些问题。
I am properly specify the build commands as far as I know as,
据我所知，我正确指定了构建命令，
g++ -g -I /usr/lib/jvm/java-6-sun-1.6.0.26/include -I /usr/lib/jvm/java-6-sun-1.6.0.26/include/linux CallJVM.c
My intention is to actually run it using jikesrvm but to experiment this I chose to work with JVM. The error I am getting is :
我的意图是实际使用 jikesrvm 运行它，但为了对此进行试验，我选择使用 JVM。我得到的错误是：
CallJVM.c: In function ‘JNIEnv* create_vm()':
CallJVM.c:14:4: warning: deprecated conversion from string constant to ‘char*'
CallJVM.c: In function ‘void invoke_class(JNIEnv*)':
CallJVM.c:28:26: error: base operand of ‘->' has non-pointer type ‘JNIEnv'
CallJVM.c:30:21: error: base operand of ‘->' has non-pointer type ‘JNIEnv'
CallJVM.c:32:26: error: base operand of ‘->' has non-pointer type ‘JNIEnv'
CallJVM.c:32:57: error: base operand of ‘->' has non-pointer type ‘JNIEnv'
CallJVM.c:33:26: error: base operand of ‘->' has non-pointer type ‘JNIEnv'
CallJVM.c:34:8: error: base operand of ‘->' has non-pointer type ‘JNIEnv'
CallJVM.c:36:8: error: base operand of ‘->' has non-pointer type ‘JNIEnv'
I noticed the different ways of implementing in C and C++ but I think I am writing it correctly.
我注意到在 C 和 C++ 中实现的不同方式，但我认为我写的是正确的。
Edit: On compiling with gcc ,I am getting
编辑：在用 gcc 编译时，我得到
undefined reference to `JNI_CreateJavaVM'
and it is what was being prompted in eclipse but I thought my configurations are not apt.When I use ctrl+clickit takes me to referenced jni.h as well but still why it is missing reference ?
am specifically mentioning my folders on include path.
这是在 eclipse 中提示的，但我认为我的配置不合适。当我使用ctrl+click它时，我也引用了 jni.h 但仍然为什么缺少引用？我特别提到了我在包含路径上的文件夹。
回答by Andreas Fester
I noticed the different ways of implementing in C and C++ but I think I am writing it correctly.
我注意到在 C 和 C++ 中实现的不同方式，但我认为我写的是正确的。
You are using the Cvariant, but are compiling with g++, which invokes the C++compiler (even if your source file has a .cextension).
您正在使用该C变体，但正在使用进行编译g++，这会调用C++编译器（即使您的源文件具有.c扩展名）。
Either change the Cvariants like
要么更改变C体，如
(*env)->FindClass(env, ...)
to the C++variants, like
到C++变体，比如
env->FindClass(...)
or switch your compiler to gccto compile the source as Ccode.
或将编译器切换gcc为将源C代码编译为代码。
回答by Rorschach
I am putting the work around found on other SO posts..
I used straight forwardly this - "
gcc -g -I /usr/lib/jvm/java-6-sun-1.6.0.26/include -I /usr/lib/jvm/java-6-sun-1.6.0.26/include/linux -L /usr/lib/jvm/java-6-sun-1.6.0.26/jre/lib/i386/server -ljvm CallJVM.cand a.out was created. Then I need to link it with libjvm.so present in server folder as mentioned in post.
我正在解决在其他 SO 帖子上找到的工作.. 我直接使用了这个 - "
gcc -g -I /usr/lib/jvm/java-6-sun-1.6.0.26/include -I /usr/lib/jvm/java-6-sun-1.6.0.26/include/linux -L /usr/lib/jvm/java-6-sun-1.6.0.26/jre/lib/i386/server -ljvm CallJVM.c并创建了 a.out。然后我需要将它与服务器文件夹中的 libjvm.so 链接，如帖子中所述。
A very beautiful explanation has been put up here
一个非常漂亮的解释已经放在这里
