build: secp256k1 warnings not turned into errors in MSAN job #33284

1. 
   fanquake commented at 5:22 pm on September 2, 2025: member

   master (7e58c94112d061af38648808aae87c369098f44c) https://cirrus-ci.com/task/6098524451897344:

    0[06:05:23.776] Treat compiler warnings as errors ..... ON
    1<snip>
    2[06:05:24.677] [ 10%] Building CXX object src/crypto/CMakeFiles/bitcoin_crypto.dir/sha256_avx2.cpp.o
    3[06:05:24.678] /ci_container_base/src/secp256k1/src/tests.c:6049:34: warning: variable 'pubkey' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer]
    4[06:05:24.678]  6049 |     SECP256K1_CHECKMEM_UNDEFINE(&pubkey, sizeof(pubkey));
    5[06:05:24.678]       |                                  ^~~~~~
    6[06:05:24.678] 1 warning generated.
    7[06:05:24.679] /ci_container_base/src/secp256k1/src/tests.c:6049:34: warning: variable 'pubkey' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer]
    8[06:05:24.679]  6049 |     SECP256K1_CHECKMEM_UNDEFINE(&pubkey, sizeof(pubkey));
    9[06:05:24.679]       |                                  ^~~~~~
   10[06:05:24.679] 1 warning generated.
   

2. 
   jmoik commented at 12:04 pm on September 3, 2025: none

   I will take a look at this
3. 
   maflcko commented at 12:22 pm on September 3, 2025: member

   The reason is that Werror is not passed down, so I guess the question is: What flags should be passed down under what circumstances?
4. 
   fanquake commented at 12:33 pm on September 3, 2025: member

   My expectation would be that the CI shouldn’t produce any spurious output, and any unexpected output would be an error. That way, any output is either fixed, or documented/suppressed. Otherwise anyone looking at the CI can’t know what is expected, what should be fixed, or what doesn’t matter, and we avoid issues like this, #33256, etc.
5. 
   jmoik commented at 12:37 pm on September 3, 2025: none

   from CmakeLists.txt: The core_interface library aims to encapsulate common build flags. It is a usage requirement for all targets except for secp256k1, which gets its flags by other means.

   We can simply add a section for WERROR to the cmake file just like for other flags like BUILD_TESTS, to inherit the WERROR setting.

6. 
   jmoik commented at 12:57 pm on September 3, 2025: none

   I actually cannot reproduce the exact warning of this macro, not on clang or g++. But adding an explicitly undefined variable produces a warning and is properly turned into an error with -DWERROR=ON after adding the inheritance.
7. hebasto added the label Build system on Sep 18, 2025
8. 
   hebasto commented at 12:55 pm on September 18, 2025: member

   Related: https://github.com/bitcoin-core/secp256k1/pull/1750.

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fanquake jmoik maflcko hebasto

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