From 13eba3d8429f641b086376a6998a3df3e5245637 Mon Sep 17 00:00:00 2001
From: WalkingDevFlag <panditrao.sid@gmail.com>
Date: Mon, 19 Jan 2026 15:28:15 +0530
Subject: [PATCH] cmake: relax CUDA version check to major.minor in
 OpenCVConfig (#26965)

The first-class-language OpenCV CMake config (OpenCVConfig-CUDALanguage.cmake.in)
pinned the consumer's CUDA Toolkit to the exact patch version OpenCV was built
with (e.g. 12.3.107), via find_package(CUDAToolkit ... EXACT) and a full
VERSION_EQUAL check. Patch versions change frequently while the CUDA runtime API
is stable within a minor release, so this forced needless rebuilds and could
FATAL_ERROR even for a matching toolkit.

Per the core team's direction on #26966, the change lives in the installed
config template rather than the build scripts, and is controlled by a
consumer-set variable:

- Default: match major.minor only (fixes the reported patch-pinning bug).
- OPENCV_STRONG_CUDA_VERSION_CHECK: restore the exact full-version match.

The build-time detection (OpenCVDetectCUDALanguage.cmake) is left untouched, so
OpenCV_CUDA_VERSION still records the full version for diagnostics.

Fixes #26965
---
 .../OpenCVConfig-CUDALanguage.cmake.in        | 37 +++++++++++++++----
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/cmake/templates/OpenCVConfig-CUDALanguage.cmake.in b/cmake/templates/OpenCVConfig-CUDALanguage.cmake.in
index 259141006a..44d8de8225 100644
--- a/cmake/templates/OpenCVConfig-CUDALanguage.cmake.in
+++ b/cmake/templates/OpenCVConfig-CUDALanguage.cmake.in
@@ -10,6 +10,14 @@ set(OpenCV_CUDNN_VERSION    "@CUDNN_VERSION@")
 set(OpenCV_USE_CUDNN        "@HAVE_CUDNN@")
 set(ENABLE_CUDA_FIRST_CLASS_LANGUAGE  ON)
 
+# By default OpenCV only requires the consumer's CUDA Toolkit to match the
+# major.minor version it was built with. The CUDA runtime API is stable within
+# a minor release and patch versions change frequently, so pinning the patch
+# component forces needless rebuilds (issue #26965). Set
+# OPENCV_STRONG_CUDA_VERSION_CHECK before find_package(OpenCV) to require an
+# exact match including the patch component.
+string(REGEX MATCH "^[0-9]+\\.[0-9]+" OpenCV_CUDA_VERSION_MAJOR_MINOR "${OpenCV_CUDA_VERSION}")
+
 if(NOT CUDAToolkit_FOUND)
   if(NOT CMAKE_VERSION VERSION_LESS 3.18)
     if(UNIX AND NOT CMAKE_CUDA_COMPILER AND NOT CUDAToolkit_ROOT)
@@ -17,15 +25,28 @@ if(NOT CUDAToolkit_FOUND)
       set(CUDA_PATH "/usr/local/cuda" CACHE INTERNAL "")
       set(ENV{CUDA_PATH} ${CUDA_PATH})
     endif()
-    find_package(CUDAToolkit ${OpenCV_CUDA_VERSION} EXACT REQUIRED)
+    if(OPENCV_STRONG_CUDA_VERSION_CHECK)
+      find_package(CUDAToolkit ${OpenCV_CUDA_VERSION} EXACT REQUIRED)
+    else()
+      find_package(CUDAToolkit ${OpenCV_CUDA_VERSION_MAJOR_MINOR} REQUIRED)
+    endif()
   else()
     message(FATAL_ERROR "Using OpenCV compiled with CUDA as first class language requires CMake \>= 3.18.")
   endif()
-else()
-  if(CUDAToolkit_FOUND)
-    set(CUDA_VERSION_STRING ${CUDAToolkit_VERSION})
-  endif()
-  if(NOT CUDA_VERSION_STRING VERSION_EQUAL OpenCV_CUDA_VERSION)
-      message(FATAL_ERROR "OpenCV library was compiled with CUDA ${OpenCV_CUDA_VERSION} support. Please, use the same version or rebuild OpenCV with CUDA ${CUDA_VERSION_STRING}")
-  endif()
+endif()
+
+if(CUDAToolkit_FOUND)
+  set(CUDA_VERSION_STRING ${CUDAToolkit_VERSION})
+endif()
+
+string(REGEX MATCH "^[0-9]+\\.[0-9]+" CUDA_VERSION_STRING_MAJOR_MINOR "${CUDA_VERSION_STRING}")
+if(OPENCV_STRONG_CUDA_VERSION_CHECK)
+  set(__ocv_cuda_found "${CUDA_VERSION_STRING}")
+  set(__ocv_cuda_built "${OpenCV_CUDA_VERSION}")
+else()
+  set(__ocv_cuda_found "${CUDA_VERSION_STRING_MAJOR_MINOR}")
+  set(__ocv_cuda_built "${OpenCV_CUDA_VERSION_MAJOR_MINOR}")
+endif()
+if(NOT __ocv_cuda_found VERSION_EQUAL __ocv_cuda_built)
+  message(FATAL_ERROR "OpenCV library was compiled with CUDA ${OpenCV_CUDA_VERSION} support. Please, use the same version or rebuild OpenCV with CUDA ${CUDA_VERSION_STRING}")
 endif()