How do you statically link libm for a native mpy file

[hlovatt]

Hi,

I'm having trouble making an mpy file from C source that uses math functions. Without math it works, e.g. factorial example from Native machine code in .mpy files. The errors I'm getting are:

CC dsp.c
LINK build/dsp.o
LinkError: build/dsp.o: undefined symbol: sinf
build/dsp.o: undefined symbol: cosf
build/dsp.o: undefined symbol: __mulsc3
build/dsp.o: undefined symbol: cabsf
build/dsp.o: undefined symbol: sqrtf
make: *** [build/dsp.native.mpy] Error 1

I suspect I have to statically link the libm library, my makefile is:

# Cross-platform Home directory definition
ifeq ($(OS),Windows_NT)
    HOME_DIR := $(HOMEDRIVE)$(HOMEPATH)
else
    HOME_DIR := $(HOME)
endif

# Location of top-level MicroPython directory - can't use ~
MPY_DIR = $(HOME_DIR)/repos/micropython

# Name of module
MOD = dsp

# Source files (.c or .py)
SRC = dsp.c

# Architecture to build for (x86, x64, armv6m, armv7m, xtensa, xtensawin, rv32imc, rv64imc)
ARCH = armv7emsp

# Force static linking for libm, then return to dynamic for everything else (from Google Gemini)
LDFLAGS = -Wl,-Bstatic -lm -Wl,-Bdynamic

# Include to get the rules for compiling and linking the module
include $(MPY_DIR)/py/dynruntime.mk

The idea, from Gemini, is to use LDFLAGS but that doesn't work :(.

Any suggestions?

Thanks in advance.

[GitHubsSilverBullet]

From the docs:

The native module is not automatically linked against the standard static libraries like libm.a and libgcc.a, which can lead to undefined symbol errors. You can link the runtime libraries by setting LINK_RUNTIME = 1 in your Makefile. Custom static libraries can also be linked by adding MPY_LD_FLAGS += -l path/to/library.a. Note that these are linked into the native module and will not be shared with other modules or the system.

[hlovatt]

Many thanks. I missed that in the documentation! For the record, in case anyone else has this issue, I also had to add to my code:

#include <errno.h>

int *__errno(void) {
    return &errno;
}

Thanks again.