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CT-NG: floating point support in Newlibs printf?


I have successfully compiled a toolchain for my ARM7TDMI with crosstool-NG 1.8.1. I have used GCC 4.5.0, Newlib 1.18 and Binutils 2.20.1, disabled EABI and software floating point. The full build.log.bz2 can be downloaded from

I can compile my codebase with no errors, but I am having trouble when trying to use printf and siblings with floating point values. Everything else, including printf's with integers, seems to work as expected. With a simple test code like this:

void float_test(void) {
    double a, b;
    int result;

    a = 12.8;
    b = 35.2;
    result = (int) (b / a);
    printf("a is %f\r\n", a);
    printf("b is %f\r\n", b);
    printf("b / a = %d\r\n", result);

My output is:
a is -0.000000
b is -0.000000
b / a = 2

So the calculations appear to be correct, but the floating point output is obviously wrong.

If I try to use e.g. %.1f in my format string, newlib calls sbrk with a ~1 GiB increment and my system naturally crashes.

I have tried to enable EABI, but I face the same problem. As far as I can figure out, newlib does support floating point values in printf, if not explicitly disabled, but I see no trace of this in the build log.

Any good advice on what I should do? The help is really appreciated. If you need additional information, just let me know.

Thank you in advance.


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