JNI call changes Fortran program behavior dependent on locale

Question

Hello,
we observed a strange problem with a Fortran code calling Java methods via JNI. The code is reading strings (e.g. 2.726), converting them into double values. Until Java7 everything was fine with this code, but since Java7 the double values were suddenly cut to what appeared to us as integer values as soon as JNI_CreateJavaVM was called. Changing between Java6 and 7 (libjvm) really made the difference. Looking into the problem we now noticed that under Java7 the behaviour is dependent on the system locale. When we used de_DE the values were cut, under POSIX,C,en_US etc. they were converted properly. This dependency was not existing in Java6. We created a testcase to reproduce this problem, which can be found here: http://planck.mpa-garching.mpg.de/testcase.tgz - just modify JAVAPATH in the Makefile and run it.
Our temporary solution is to make sure that LC_ALL (or more specific LC_NUMERIC) is set to a working value, but we wonder if this is a bug which was introduced recently or if this is intended.
Best regards.

Answer 1

OK, I will explain in detail what we are doing (basically our testcase):
We have a Fortran program which defines a character and a double variable. We fill the char with "2.726". Convert this via Fortran read Method to double. Print the resulting double, which is 2.726.
Now we call a C Wrapper which does nothing else than just creating a JVM.
We do the same test as above in the Fortran program, just now the resulting double value is 2.000
To prevent misunderstandings, I will also copy the code of both programs here:
Fortran:
character(len=4096)::tstr
double precision tdbl
tstr="2.726"
read (tstr,*) tdbl
print *,"before JVM creation: result=",tdbl
call cfunc
tstr="2.726"
read (tstr,*) tdbl
print *,"after JVM creation: result=",tdbl
end program
C part:
#include <jni.h>
JavaVM *jvm;
JNIEnv *env;
int cfunc()
JavaVMInitArgs vm_args;
JavaVMOption options[1];
options[0].optionString = "-Djava.compiler=NONE";           /* disable JIT */
vm_args.version = JNI_VERSION_1_4;
vm_args.options = options;
vm_args.nOptions = 1;
vm_args.ignoreUnrecognized = 0;
JNI_CreateJavaVM(&jvm, (void **)&env, &vm_args);
return 0;