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bitcoin-core / secp256k1

Optimized C library for EC operations on curve secp256k1
MIT License
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cmake: Add `--no-undefined` linker option #1559

Open hebasto opened 1 week ago

hebasto commented 1 week ago

This PR adds the --no-undefined option to a linker, which supports it.

From the GNU ld docs:

--no-undefined

Report unresolved symbol references from regular object files. This is done even if the linker is creating a non-symbolic shared library.

Closes https://github.com/bitcoin-core/secp256k1/issues/1556.

~Looking for Concept (N)ACKs. Once ACKed, I'll add the same functionality to the Autotools-based build system.~

theuni commented 1 week ago

Concept ACK.

I think we might be after -Wl,--no-allow-shlib-undefined, though, and only for the shared lib as that's what we care about. --no-undefined is strictly stronger, I guess, and should also be satisfied for the binaries. So I suppose the sledgehammer approach here should be fine.

hebasto commented 1 week ago

I think we might be after -Wl,--no-allow-shlib-undefined...

From my experience, it fails to catch an issue like one I demoed in https://github.com/bitcoin-core/secp256k1/issues/1556.

real-or-random commented 1 week ago

I think we might be after -Wl,--no-allow-shlib-undefined, though, and only for the shared lib as that's what we care about. --no-undefined is strictly stronger, I guess, and should also be satisfied for the binaries. So I suppose the sledgehammer approach here should be fine.

If https://stackoverflow.com/a/2356407 is right, then --no-undefined covers objects created by the linker and --no-allow-shlib-undefined covers shared libraries consumed by the linker.

real-or-random commented 1 week ago

Concept ACK

hebasto commented 1 week ago

Looking for Concept (N)ACKs. Once ACKed, I'll add the same functionality to the Autotools-based build system.

Added a commit for the Autotools-based build system.

hebasto commented 1 week ago

I think we need to make add an exception to this if external default callbacks are enabled because the entire point of this option is that the user provides the callbacks at link time.

Right. I did it in CMake, but forgot about it in Autotools. Fixed.