cmake: configure libsecp256k1.pc during install #1692

1. 
   purpleKarrot commented at 5:10 pm on June 27, 2025: contributor

   When installing to a given prefix, make sure that the .pc file contains that prefix rather than the value of CMAKE_INSTALL_PREFIX that the project was configured with.
2. cmake: configure libsecp256k1.pc during install

   When installing to a given prefix, make sure that the .pc file contains
   that prefix rather than the value of CMAKE_INSTALL_PREFIX that the
   project was configured with.

   7106dce6fd
3. real-or-random added the label bug on Jun 27, 2025
4. real-or-random added the label build on Jun 27, 2025
5. 
   real-or-random commented at 6:29 pm on June 27, 2025: contributor

   Thanks! Can you provide instructions for a test case that is fixed by this?

   cc @hebasto

6. 
   hebasto commented at 7:45 pm on June 27, 2025: member

   cc @hebasto

   I haven’t tested this PR yet, but the issue I reported to @purpleKarrot offline can be reproduced on the master branch as follows:

    0$ cmake -B build
    1$ cmake --build build
    2$ install_dir=$(mktemp -d)
    3$ cmake --install build --prefix $install_dir
    4$ cat ${install_dir}/lib/pkgconfig/libsecp256k1.pc 
    5prefix=/usr/local
    6exec_prefix=${prefix}
    7libdir=${exec_prefix}/lib
    8includedir=${prefix}/include
    9
   10Name: libsecp256k1
   11Description: Optimized C library for EC operations on curve secp256k1
   12URL: https://github.com/bitcoin-core/secp256k1
   13Version: 0.6.1
   14Cflags: -I${includedir}
   15Libs: -L${libdir} -lsecp256k1
   

   Note prefix=/usr/local, which is obviously incorrect.

7. 
   purpleKarrot commented at 8:47 pm on June 27, 2025: contributor

   What @hebasto wrote.

   Also, when testing this, try installing as root and then verify whether you can delete the build directory with non-root permission. Also, try installing twice in a row and verify that the second install does not modify the timestamp of the file.

8. real-or-random approved
9. 
   real-or-random commented at 6:12 am on June 30, 2025: contributor

   ACK 7106dce6fd410043fc297139c6307cb6016d2a7b I verified that it fixes the path in libsecp256k1.pc
10. real-or-random merged this on Jun 30, 2025
11. real-or-random closed this on Jun 30, 2025

    ---

12. purpleKarrot deleted the branch on Jun 30, 2025
13. 
    hebasto commented at 12:20 pm on June 30, 2025: member

    While working on this issue earlier, I also considered support for relative paths.

    I’m not sure how important this case is, but the current solution does not handle relative paths correctly. Consider the following examples:

    • using CMAKE_INSTALL_PREFIX during configuration:

    0$ cmake -B build -DCMAKE_INSTALL_PREFIX=../install/a
    1$ cmake --build build
    2$ cmake --install build
    3$ cat ../install/a/lib/pkgconfig/libsecp256k1.pc | head -1
    4prefix=/home/hebasto/dev/secp256k1/install/a
    

    • using the --prefix option during installation:

    0$ cmake -B build
    1$ cmake --build build
    2$ cmake --install build --prefix ../install/b
    3$ cat ../install/b/lib/pkgconfig/libsecp256k1.pc | head -1
    4prefix=../install/b
    

14. hebasto referenced this in commit 68094d6972 on Jun 30, 2025
15. 
    purpleKarrot commented at 2:47 pm on June 30, 2025: contributor

    @real-or-random, what @hebasto shows is a severe regression for the use case of creating packages. When building binary packages for distribution, you usually install to a temporary directory and then create a tarball of that directory. Since pkg-config does not support relocatable packages, the .pc file needs to contain the location where the tarball will be extracted to, not the location that cmake installs to. The builtin default of /usr/local or the value of CMAKE_INSTALL_PREFIX is actually more correct than the argument to cmake --install.
16. josibake referenced this in commit bb0dc6d75c on Jul 10, 2025
17. josibake referenced this in commit 90b6c9e668 on Jul 11, 2025
18. josibake referenced this in commit 4340be2236 on Jul 14, 2025
19. josibake referenced this in commit 3a3815d5ee on Jul 16, 2025
20. 
    fanquake commented at 12:24 pm on July 16, 2025: member

    Reverted in #1694.

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purpleKarrot real-or-random hebasto fanquake

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