This sounds more like a miscompilation to me, but i don't know what hardware that router is.

I'm closing this for now since it works for me (see below). Don't hesitate to reopen if you can provide more detail.

thanks,

$ gcc -Os strtold.c && ./a.out
Lg=2
g =2
f =2.000000
$ cat strtold.c 
#include <stdlib.h>
#include <stdio.h>
int main(void) {
	printf("Lg=%Lg\n", strtold("2.0000", NULL));
	printf("g =%g\n", strtod("2.0000", NULL));
	printf("f =%f\n", strtof("2.0000", NULL));
	return 0;
}

I also can confirm erroneous strtold() output on MIPS32 LE platform. Your sample produces output like:

$ ./strtold
Lg=2.122e-314
g =2
f =0.000000

toolchain used: gcc is 4.2.4, uClibc 0.9.30.1, binutils 2.19.1

If I changes example like:

#include <stdlib.h>
#include <stdio.h>

int main(void) {
        long double ld = 0;
        float f = 0;

        ld = strtold("2.0000", NULL);
        f = strtof("2.0000", NULL);

        printf("Lg=%Lg\n", ld);
        printf("g =%g\n", strtod("2.0000", NULL));
        printf("f =%f\n", f);

        return 0;
}

output will be:

$ ./strtold
Lg=7.16427e+08
g =2
f =716427264.000000

Sorry, this is a kind of miscompilation bug - according to strtold manual, it REQUIRES even for glibc:

==========================================================================
  Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

    strtof(),  strtold():  _XOPEN_SOURCE >= 600   ||   _ISOC99_SOURCE;   or
    cc -std=c99
==========================================================================
I simply forgot to provide -std=c99 when compiling test-case, so please close the bug.