如何在Bazel中实现类似CMake的add_definitions功能（CUDA检测场景）

Got it, let's walk through how to replicate that CMake CUDA check and preprocessor definition logic in Bazel—this is actually straightforward once you know the built-in tools Bazel provides.

Step 1: Use Bazel's Built-in CUDA Condition #

Bazel has a native conditional flag @bazel_tools//tools/cuda:is_cuda_enabled that automatically detects whether your system has a working CUDA setup (including the nvcc compiler, CUDA libraries, etc.). You’ll use this with Bazel’s select() function to toggle the WITH_CUDA preprocessor definition.

Step 2: Apply the Definition to Your Targets #

In your BUILD file, add the defines field to your cc_library or cc_binary targets, using select() to conditionally enable -DWITH_CUDA based on CUDA availability:

cc_library(
    name = "my_cuda_aware_lib",
    srcs = ["my_source.cpp"],
    # Conditionally define WITH_CUDA only if CUDA is detected
    defines = select({
        "@bazel_tools//tools/cuda:is_cuda_enabled": ["WITH_CUDA"],
        "//conditions:default": [],
    }),
    # Optional: Link against CUDA libraries if your code needs them
    deps = select({
        "@bazel_tools//tools/cuda:is_cuda_enabled": ["@bazel_tools//tools/cuda:cuda"],
        "//conditions:default": [],
    }),
)

Step 3: Keep Your Existing Conditional Compilation Code #

You don’t need to change anything in your source code—your existing #ifdef WITH_CUDA checks will work exactly as they did with CMake:

#ifdef WITH_CUDA
// CUDA-specific implementation here
#include <cuda_runtime.h>
#else
// Fallback CPU-only code
#endif

Notes for Edge Cases #

• If Bazel fails to detect your CUDA installation automatically, you can explicitly point it to the CUDA path with either:
  • The command-line flag: bazel build --cuda_path=/path/to/your/cuda
  • The CUDA_PATH environment variable
• For project-wide definitions (not always recommended, as it affects all targets), you can create a shared cc_library with the conditional defines and have all other targets depend on it.

内容的提问来源于stack exchange，提问作者superd