Scope CUDA link deps to their targets in meson.build

.github/workflows/build.yml

@@ -102,6 +102,60 @@ jobs:
           pixi r pytest
           rm -rf build/
 
+  build_gpu:
+    # Build-only: linking against cuBLAS/cuSPARSE needs the CUDA toolkit but
+    # not a physical GPU, so this validates the use_gpu build/link path without
+    # running the solver (running would require GPU hardware).
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        shell: bash -l {0}
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: [ "3.12" ]
+
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          submodules: recursive
+      - uses: prefix-dev/setup-pixi@v0.10.0
+        with:
+          cache: false
+          pixi-version: v0.46.0
+      - name: Add .pixi/envs/default to the $PATH
+        run: echo "$(pwd)/.pixi/envs/default/bin" >> $GITHUB_PATH
+        shell: bash
+      - name: Install dependencies
+        run: |
+          pixi add --platform linux-64 scipy numpy pip pytest meson meson-python \
+            openblas python==${{ matrix.python-version }} \
+            cuda-version=12.* cuda-nvcc cuda-cudart-dev libcublas-dev libcusparse-dev
+      - name: Build (use_gpu=true)
+        run: |
+          export CUDA_PATH="$(pwd)/.pixi/envs/default"
+          export CUDA_HOME="$CUDA_PATH"
+          pixi r python -m pip install -v . --no-build-isolation \
+            -Csetup-args=-Duse_gpu=true -Csetup-args=-Dint32=true
+      - name: Check _scs_gpu is linked against cuBLAS and cuSPARSE
+        # A shared library links successfully even with undefined symbols, so the
+        # real regression test is that libcublas/libcusparse are recorded as
+        # NEEDED entries (the bug fixed in #221 was a missing link, seen only at
+        # import time as `undefined symbol: cusparseDestroySpMat`).
+        run: |
+          # Locate the installed extension in the pixi env's site-packages.
+          so=$(find "$(pwd)/.pixi/envs/default/lib" -name '_scs_gpu*.so' | head -1)
+          if [ -z "$so" ]; then
+            echo "ERROR: _scs_gpu*.so not found in the pixi environment"
+            find "$(pwd)/.pixi/envs/default/lib" -name '_scs_*.so' || true
+            exit 1
+          fi
+          echo "Inspecting $so"
+          readelf -d "$so"
+          readelf -d "$so" | grep -q 'libcublas' || { echo "ERROR: _scs_gpu not linked against cuBLAS"; exit 1; }
+          readelf -d "$so" | grep -q 'libcusparse' || { echo "ERROR: _scs_gpu not linked against cuSPARSE"; exit 1; }
+          echo "OK: _scs_gpu links cuBLAS and cuSPARSE"
+
   build_native_arch:
     runs-on: ubuntu-latest
     defaults:

meson.build

@@ -287,17 +287,18 @@ endif
 
 if get_option('use_gpu')
   gpu_c_args = common_c_args + ['-DPY_GPU=1', '-DINDIRECT=1']
-  _deps += cuda_dep
   cublas_dep = cc.find_library('cublas', required: false)
   if not cublas_dep.found()
     cublas_dep = dependency('cublas', required: true)
   endif
-  _deps += cublas_dep
   cusparse_dep = cc.find_library('cusparse', required: false)
   if not cusparse_dep.found()
     cusparse_dep = dependency('cusparse', required: true)
   endif
-  _deps += cusparse_dep
+  # Scope the CUDA libraries to this target rather than mutating the shared
+  # `_deps`, so they don't leak into _scs_mkl / _scs_accelerate / _scs_cudss
+  # when use_gpu is combined with those backends.
+  gpu_deps = _deps + [cuda_dep, cublas_dep, cusparse_dep]
   if get_option('gpu_atrans')
     gpu_c_args += '-DGPU_TRANSPOSE_MAT=1'
   endif
@@ -310,10 +311,12 @@ if get_option('use_gpu')
     # In Meson, sources with a `.cu` extension are compiled with nvcc by default.
     # To compile `.c` files with nvcc, they must be explicitly targeted.
     # It is strongly recommended to rename CUDA-C files to `.cu`.
+    # Meson's fs module has no glob(), so these are listed explicitly; keep in
+    # sync with the .c files under scs_source/linsys/gpu{,/indirect}.
     'scs_source/linsys/gpu/gpu.c',
     'scs_source/linsys/gpu/indirect/private.c',
     c_args: gpu_c_args,
-    dependencies: _deps,
+    dependencies: gpu_deps,
     include_directories: [
       common_includes, 'scs_source/linsys/gpu/', 'scs_source/linsys/gpu/indirect'
     ],
@@ -382,9 +385,10 @@ if host_machine.system() == 'darwin'
 endif
 
 if get_option('link_cudss')
-  _deps += cuda_dep
   cudss_dep = dependency('cudss', required: true)
-  _deps += cudss_dep
+  # Scope the CUDA libraries to this target rather than mutating the shared
+  # `_deps` (see the use_gpu block above).
+  cudss_deps = _deps + [cuda_dep, cudss_dep]
   py.extension_module(
     '_scs_cudss',
     'scs/scspy.c',
@@ -394,7 +398,7 @@ if get_option('link_cudss')
     spectral_cone_sources,
     c_args: common_c_args + ['-DPY_CUDSS'],
     include_directories: common_includes + ['scs_source/linsys/cudss/direct'],
-    dependencies: _deps,
+    dependencies: cudss_deps,
     install_dir: scs_dir,
     install: true,
   )