mypyc-compiled extensions missing math library linking causing undefined symbol errors

Bug Report
When building mypy with mypyc enabled (MYPY_USE_MYPYC=1), the compiled C extensions are missing explicit linking to the math library (libm), causing undefined symbol errors for standard math functions.

[./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so]:
    linux-vdso.so.1 (0x0000ffffb4c9c000)
    libc.so.6 => /lib64/libc.so.6 (0x0000ffffb4632000)
    /lib/ld-linux-aarch64.so.1 (0x0000ffffb4c4f000)
undefined symbol: sin	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: cos	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: tan	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: sqrt	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: exp	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: fmod	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: pow	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: log	(./lib/python3.12/site-packages/30fcd23745efe32ce681__mypyc.cpython-312-aarch64-linux-gnu.so)

[./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so]:
    linux-vdso.so.1 (0x0000ffff80b96000)
    libc.so.6 => /lib64/libc.so.6 (0x0000ffff7ee32000)
    /lib/ld-linux-aarch64.so.1 (0x0000ffff80b49000)
undefined symbol: sin	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: cos	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: tan	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: sqrt	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: exp	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: fmod	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: pow	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)
undefined symbol: log	(./lib/python3.12/site-packages/3204bda914b7f2c6f497__mypyc.cpython-312-aarch64-linux-gnu.so)

To Reproduce

PACKAGE_VERSION="v1.19.1"
ARCHIVE_NAME="${PACKAGE_VERSION}.tar.gz"
curl -fLO "https://github.com/python/mypy/archive/refs/tags/${ARCHIVE_NAME}"
tar xf "${ARCHIVE_NAME}"
cd "mypy-${PACKAGE_VERSION#v}"

export MYPY_USE_MYPYC="1"
pip3 install . -v -v -v --compile --no-deps --no-cache-dir --no-build-isolation --no-binary :all:

Expected Behavior
No unexpected undefined symbols

Actual Behavior

Unexpected undefined symbols

Your Environment

• OS: Amz Linux 2023 aarch64
• Python: 3.12.7
• mypy: 1.19.1

Proposed Solution

The math library needs to be added to the extension modules during the build process. A potential patch location is in setup.py after the extensions are created:

# After mypyc_build_ext() creates ext_modules, add math library
for ext in ext_modules:
    if "m" not in ext.libraries:
        ext.libraries.append("m")

However, this approach may over-link modules that don't need libm. A more precise solution would require:

1. Identifying which specific mypyc-generated extensions actually use math functions
2. Only adding -lm to those specific extensions
3. This may require changes in mypyc itself to track which C math functions are used during compilation

Temporary Workaround is:

# Patch setup.py to add math library to all extensions
sed -i '
/log_trace=log_trace,$/,/^    assert ext_modules$/ {
    /^    )$/ a\
\
    for ext in ext_modules:\
        if "m" not in ext.libraries:\
            ext.libraries.append("m")
}
' "./setup.py"

Inizia in setup.py, nelle vicinanze di mypyc_build_ext() e della creazione di ext_modules, quindi riproduci la compilazione con MYPY_USE_MYPYC=1 usando il comando pip documentato nell’ambiente interessato. Determina quali estensioni generate richiedono libm e assicurati che le estensioni compilate vengano caricate senza simboli matematici non definiti, evitando quando possibile il linking non necessario.