警告：使用了“ void checkGlError（const char *）”，但从未定义

Question

I'm compiling a Shared library using Android NDK r6b. All classes are C++.

I have the following two classes:

Utils.hpp

#ifdef USE_OPENGL_ES_1_1
#include <GLES/gl.h>
#include <GLES/glext.h>
#else
#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>
#endif
#include <android/log.h>

// Utility for logging:
#define LOG_TAG    "ROTATEACCEL"
#define LOG(...)  __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
#define  LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

#ifdef __cplusplus
extern "C" {
#endif

static void checkGlError(const char* op);

#ifdef __cplusplus
}
#endif

Utils.cpp

#include "Utils.hpp"

#ifdef __cplusplus
extern "C" {
#endif

static void checkGlError(const char* op) {
    for (GLint error = glGetError(); error; error
            = glGetError()) {
        LOGI("after %s() glError (0x%x)\n", op, error);
    }
}

#ifdef __cplusplus
}
#endif

When I want to use this function in other C++ files I #include "Utils.hpp" . But, in those files I get an error:

undefined reference to `checkGlError'

Why am I getting this warning?

Answer 1

You've made it static . It only lives in that specific translation unit therefore. The solution is to remove the static keyword.

The warning is telling you that in the header file you "promised" there would be a definition in that translation unity if one was needed, but one has not been provided and it was needed.

Answer 2

static void checkGlError(const char* op);

It is a static function, that means, it has internal linkage, and therefore cannot be called from another translation unit.

Remove the static keyword from it's declaration as well as from it's definition, and it would work fine.