mingw-w64: “visibility attribute not supported in this configuration; ignored” under -flto #1421

1. 
   fanquake commented at 1:43 pm on September 6, 2023: member

   Building master (b10ddd2bd2bdce9ca8f2d4733636a9d9e7ac3da1):

    0# x86_64-w64-mingw32-gcc (GCC) 12-win32
    1./autogen.sh
    2./configure --host=x86_64-w64-mingw32 CFLAGS="-flto" LDFLAGS="-flto"
    3make -j9
    4<snip>
    5src/secp256k1.c: In function 'secp256k1_context_create':
    6src/secp256k1.c:149:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
    7  149 | }
    8      | ^
    9src/secp256k1.c: In function 'secp256k1_context_preallocated_clone':
   10src/secp256k1.c:160:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
   11  160 | }
   12      | ^
   13src/secp256k1.c: In function 'secp256k1_context_clone':
   14src/secp256k1.c:173:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
   15  173 | }
   16      | ^
   17src/secp256k1.c: In function 'secp256k1_context_preallocated_destroy':
   18src/secp256k1.c:184:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
   19  184 | }
   20      | ^
   21src/secp256k1.c: In function 'secp256k1_context_destroy':
   22src/secp256k1.c:196:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
   23  196 | }
   24      | ^
   25src/secp256k1.c: In function 'secp256k1_ec_pubkey_parse':
   26src/secp256k1.c:288:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
   27  288 | }
   28      | ^
   29src/secp256k1.c: In function 'secp256k1_ec_pubkey_serialize':
   30src/secp256k1.c:311:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
   31  311 | }
   32      | ^
   33< similar output continues>
   

   Wanted to raise this, as Core may eventually go down the LTO route (https://github.com/bitcoin/bitcoin/pull/25391), and -flto will be getting passed down.

2. 
   real-or-random commented at 5:05 pm on September 6, 2023: contributor

   Hm, thanks. It’s a bit mysterious that this happens only with -flto and only when compiling tests or noverify_tests, but for example not in the exhaustive_tests. But okay, whatever, apparently we hit that line here, which is supposed to be active only when not on Windows: https://github.com/bitcoin-core/secp256k1/blob/b10ddd2bd2bdce9ca8f2d4733636a9d9e7ac3da1/include/secp256k1.h#L159-L161

   We should probably just have a SECP256K1_TESTS #define and if this is defined, set nothing for symbol visibility.

3. real-or-random added the label build on Sep 6, 2023
4. 
   real-or-random commented at 5:05 pm on September 6, 2023: contributor

   cc @hebasto , any further ideas here?
5. 
   hebasto commented at 10:49 am on September 8, 2023: member

   cc @hebasto , any further ideas here?

   I’m looking into it.

   ---

   Just a note about building with LTO using CMake:

   0cmake -B build -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON --toolchain cmake/x86_64-w64-mingw32.toolchain.cmake
   1cmake --build build
   

6. 
   hebasto commented at 1:50 pm on September 8, 2023: member

   The -flto-partition=1to1 option helps:

   0$ x86_64-w64-mingw32-gcc --version
   1x86_64-w64-mingw32-gcc (GCC) 12-posix
   2Copyright (C) 2022 Free Software Foundation, Inc.
   3This is free software; see the source for copying conditions.  There is NO
   4warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   5
   6$ ./autogen.sh
   7$ ./configure --host=x86_64-w64-mingw32 CFLAGS="-flto -flto-partition=1to1" LDFLAGS="-flto=auto"
   8$ make -j16
   

   From GCC docs:

   …‘1to1’ can be used as an workaround for various code ordering issues…

7. 
   real-or-random commented at 3:07 pm on September 11, 2023: contributor

   The -flto-partition=1to1 option helps:

   Hm, interesting and good to know. I guess, we should still make sure the build is clean with just -lto. Any suggestions here?

8. 
   real-or-random commented at 11:33 pm on August 24, 2024: contributor

   Reported to GCC: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116478
9. real-or-random referenced this in commit a22208e1f1 on Aug 24, 2024
10. real-or-random referenced this in commit 5eb211a924 on Aug 24, 2024
11. real-or-random referenced this in commit 6077065aa3 on Aug 25, 2024
12. real-or-random referenced this in commit 447334cb06 on Sep 17, 2024
13. real-or-random closed this on Oct 21, 2024

    ---

14. real-or-random referenced this in commit f0868a9b3d on Oct 21, 2024

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fanquake real-or-random hebasto

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