FTBFS: opencv fails to build on riscv64

[Heinrich Schuchardt]

A build failure occurs when building OpenCV on riscv64:
https://launchpad.net/ubuntu/+source/opencv/4.10.0+dfsg-6ubuntu1/+build/31403356

/<<PKGBUILDDIR>>/modules/core/include/opencv2/core/hal/intrin_rvv.hpp: In function ‘void cv::hal_baseline::v_rshr_pack_u_store(uchar*, const v_int16x8&)’:
/<<PKGBUILDDIR>>/modules/core/include/opencv2/core/hal/intrin_rvv_010_compat_non-policy.hpp:18935:53: error: too few arguments to function ‘vuint8m1_t __riscv_vnclipu_wx_u8m1(vuint16m2_t, long unsigned int, unsigned int, long unsigned int)’ [-Wtemplate-body]
18935 | #define vnclipu_wx_u8m1(...) __riscv_vnclipu_wx_u8m1(__VA_ARGS__)
      | ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
/<<PKGBUILDDIR>>/modules/core/include/opencv2/core/hal/intrin_rvv.hpp:2492:25: note: in expansion of macro ‘vnclipu_wx_u8m1’
 2492 | v_store(ptr, _Tpvec(rshr(cast(vmax_vx_##suffix##m2(vle##width##_v_##suffix##m2(arr, vl), 0, vl)), n, vl))); \
      | ^~~~
/<<PKGBUILDDIR>>/modules/core/include/opencv2/core/hal/intrin_rvv.hpp:2495:1: note: in expansion of macro ‘OPENCV_HAL_IMPL_RVV_PACK_U’
 2495 | OPENCV_HAL_IMPL_RVV_PACK_U(v_uint8x16, uchar, v_int16x8, short, 8, 16, u8, i16, vnclipu_wx_u8m1, vreinterpret_v_i16m2_u16m2, 8, 16)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~

[Heinrich Schuchardt (xypron)]

The buildlog shows a failure is the documentation job:

error opening bib17850.bbl: No such file or directory
bibtex command failed: No such file or directory
error: Problems running bibtex. Verify that the command 'perl --version' works from the command line. Exit code: 2

[Valentin Haudiquet (vhaudiquet)]

After that bibtex error, there are a lot of RVV-related compile errors, mostly in files like
/<<PKGBUILDDIR>>/modules/core/include/opencv2/core/hal/intrin_rvv*.hpp or .cpp

I wonder if those are related or not. I will first try to fix the RVV failures, then look at BibTeX, thanks for pointing it out :)

For the RVV part, it seems that OpenCV might need some specific flags according to their documentation (https://github.com/opencv/opencv/wiki/OpenCV-RISC-V). I will investigate this further, trying builds in PPA: https://launchpad.net/~vhaudiquet/+archive/ubuntu/opencv-lp2130009/+packages

[Gianfranco Costamagna (costamagnagianfranco)]

I did force gcc-14 on riscv64 and in 6 hours the build should finish. Please wait to upload until this one is good so we have at least a build for the transition rebuilds

[Rik Mills (rikmills)]

For the record, Gianfranco's build forcing gcc-14 on riscv64 succeeded, and the package is now migrating to the resolute release pocket. Obviously this bug stays open as we need a fix that does not require such a workaround.

[Heinrich Schuchardt (xypron)]

Fixed with 4.10.0+dfsg-7ubuntu3

[Valentin Haudiquet (vhaudiquet)]

I don't believe that this is fixed, I think that one still has the workaround (building with gcc-14). But maybe we should open a separate bug for RVV enablement on OpenCV?

I must admit my previous investigations led me nowhere, so this might require more work...

[Gianfranco Costamagna (costamagnagianfranco)]

Using gcc-14 is not a fix... reopening

[Heinrich Schuchardt (xypron)]

b5ea32158a5f ("Merge pull request #25883 from hanliutong:rvv-intrin-upgrade")
in version 4.11 updated the RISC-V vector intrinsics.

35571be57089 ("Merge pull request #26318 from hanliutong:rvv-intrin-m2")
contains a further upgrade of vector intrinsics in verison 4.11.

[Heinrich Schuchardt (xypron)]

The current upstream release is 4.13.0.

[Heinrich Schuchardt (xypron)]

cmake -DWITH_HAL_RVV=OFF
allows to build without the problematic code.

[Heinrich Schuchardt (xypron)]

Testing the binaries is possible with 'make test'.

On 4.13.0 there is no difference in the number of failed tests between building with and without vector support.