Logging values of variables in Android native ndk
AndroidC++DebuggingLoggingAndroid NdkAndroid Problem Overview
I set up logging with C++ in Android NDK.
I can print a message to logcat like this:
__android_log_write(ANDROID_LOG_INFO, "tag here", "message here");
Now let's say I have an integer called testint. How can I print the value of this int?
Something like this prints the address, but I want the value. I haven't found anything in C++ on how to do this. Thanks for any help!
__android_log_print(ANDROID_LOG_INFO, "sometag", "%p", *test);
Android Solutions
Solution 1 - Android
Here's the most concise way I've seen:
#include <android/log.h>
#define LOG_TAG "someTag"
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN,LOG_TAG,__VA_ARGS__)
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
...
// Now you can log very simply like this:
int foo = 42;
LOGD( "This is a number from JNI: %d", foo );
Also, make sure you link to the log library in your Android.mk:
LOCAL_LDLIBS := -llog
Solution 2 - Android
You could use __android_log_print
which uses a sprintf
-like syntax that formats your data into a string.
__android_log_print(ANDROID_LOG_INFO, "sometag", "test int = %d", testInt);
Solution 3 - Android
Take advantage of the variadic log print function you have available. For my own code, I provide a LogInfo() function to make it simple. Of course there are several options available to you here.
void LogInfo(const char *sTag, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
__android_log_vprint(ANDROID_LOG_INFO, sTag, fmt, ap);
va_end(ap);
}
Solution 4 - Android
__android_log_print() takes a format string and a variable argument list. The format specifier you're looking for to print out a signed integer is "%d". So something like this is what you want:
int foo = 42;
__android_log_print(ANDROID_LOG_INFO, "SomeTag", "foo is %d", foo);
For more information on format strings, you can see the sprintf manual.