Oops, lost track of that bug, it also affects the standard trig functions (sin, cos, atan, etc). It's some strange linker mojo, we haven't figured it out yet to be honest. The canonical weirdness is that this code works fine:
float bar = 12.34;
void setup() { }
void loop() {
float foo = 12.34;
foo = sqrt(foo);
//bar = sqrt(bar);
Serial2.println(foo);
Serial2.println(bar);
}
but if you uncomment the bar line it doesn't work. I'm pretty sure this is because the math library isn't actually getting linked in, but in most trivial test cases the compiler optimizes out the actual function call so this wasn't found in our earlier testing.
CarlO
Member
Hi bnewbold,
After digging around the web, I found out that the code for sqrt() is supposed to be in an archived library named libm.a After trying to decipher the ArmCompiler class and the Boards.txt file, it looks like the IDE is telling the linker to look for libraries in this path:
Maple IDE\hardware\leaflabs\cores\maple
I notice there is not a copy of the libm.a library in the path that the linker is looking at.
It also looks like adding the compiler switch -lm will instruct the linker to link in the proper math library included with the compiler. This seems to be the approach that Arduino uses in it's Compiler class.
You can see an explanation here:
http://www.network-theory.co.uk/docs/gccintro/gccintro_17.html
I'm not really set up to build the IDE or I would test this out.
Carl
The fix I found is in this commit:
http://github.com/leaflabs/libmaple/commit/5f11e12d66ce65e8be2b695ece6f35c2889d2aa2
The punchline is that you can hand-modify the ram.ld and flash.ld linker scripts and add libm.a to the GROUPS() line to get the math functions linked in correctly.
libm.a is already included in the gcc toolchain, it simply wasn't added to the linker search path. This problem took a while to track down because it didn't affect our Makefile toolchain and the compiler would frequently optimize calls away. For instance this bit of code links fine:
float foo = 12.34;
void setup() {}
void loop() {
//foo = sqrt(foo);
SerialUSB.println(foo);
float bar = 56.78;
bar = sqrt(bar);
SerialUSB.println(bar);
}but if you uncomment the "foo = sqrt(foo);" line it does not link.
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