feat: add nvcc_fixed_random_seed feature for nvcc based toolchain config

.github/workflows/build-tests.yaml

@@ -101,8 +101,10 @@ jobs:
       - run: cd examples && bazelisk build --jobs=1 //if_cuda:main
       - run: cd examples && bazelisk build --jobs=1 //if_cuda:main --enable_cuda=False
       - run: bazelisk shutdown
+
       # run some repo integration tests
       - run: cd tests/integration && ./test_all.sh
+      - run: cd tests/hermeticity && ./test.sh
 
       # Use Bazel 7
       - run: echo "USE_BAZEL_VERSION=7.5.0" >> $GITHUB_ENV

cuda/private/toolchain_configs/nvcc.bzl

@@ -559,6 +559,21 @@ def _impl(ctx):
         ],
     )
 
+    # NOTE: this only works on compiler newer than 12.9
+    nvcc_fixed_random_seed_feature = feature(
+        name = "nvcc_fixed_random_seed",
+        enabled = True,
+        flag_sets = [
+            flag_set(
+                actions = [
+                    ACTION_NAMES.cuda_compile,
+                    ACTION_NAMES.device_link,
+                ],
+                flag_groups = [flag_group(flags = ["--frandom-seed=%{output_file}"])],
+            ),
+        ] if nvcc_version_ge(ctx, 12, 9) else [],
+    )
+
     cuda_device_debug_feature = feature(
         name = "cuda_device_debug",
         flag_sets = [
@@ -601,6 +616,7 @@ def _impl(ctx):
         nvcc_allow_unsupported_compiler_feature,
         nvcc_relaxed_constexpr_feature,
         nvcc_extended_lambda_feature,
+        nvcc_fixed_random_seed_feature,
         cuda_device_debug_feature,
     ]
 

cuda/private/toolchain_configs/nvcc_msvc.bzl

@@ -599,6 +599,21 @@ def _impl(ctx):
         ],
     )
 
+    # NOTE: this only works on compiler newer than 12.9
+    nvcc_fixed_random_seed_feature = feature(
+        name = "nvcc_fixed_random_seed",
+        enabled = True,
+        flag_sets = [
+            flag_set(
+                actions = [
+                    ACTION_NAMES.cuda_compile,
+                    ACTION_NAMES.device_link,
+                ],
+                flag_groups = [flag_group(flags = ["--frandom-seed=%{output_file}"])],
+            ),
+        ] if nvcc_version_ge(ctx, 12, 9) else [],
+    )
+
     cuda_device_debug_feature = feature(
         name = "cuda_device_debug",
         flag_sets = [
@@ -646,6 +661,7 @@ def _impl(ctx):
         nvcc_allow_unsupported_compiler_feature,
         nvcc_extended_lambda_feature,
         nvcc_relaxed_constexpr_feature,
+        nvcc_fixed_random_seed_feature,
         cuda_device_debug_feature,
     ]
 

tests/hermeticity/BUILD.bazel

@@ -0,0 +1,13 @@
+load("@rules_cuda//cuda:defs.bzl", "cuda_binary", "cuda_library")
+
+cuda_library(
+    name = "cuda_lib",
+    srcs = ["lib.cu"],
+    hdrs = ["lib.h"],
+)
+
+cuda_binary(
+    name = "cuda_test",
+    srcs = ["main.cu"],
+    deps = [":cuda_lib"],
+)

tests/hermeticity/lib.cu

@@ -0,0 +1,26 @@
+#include "lib.h"
+#include <iostream>
+
+namespace {
+int helper_function(OptionB method) {
+  if (method == OptionB::B) {
+    return 1;
+  }
+
+  return 1;
+}
+} // namespace
+
+template <class T> bool process(OptionA format, OptionB resizeMethod) {
+  if (format == OptionA::A) {
+    // The implementation doesn't matter, just the call to the function
+    // in the anonymous namespace.
+    helper_function(resizeMethod);
+    return true;
+  }
+
+  return false;
+}
+
+template bool process<unsigned char>(OptionA format,
+                                    OptionB resizeMethod);

tests/hermeticity/lib.h

@@ -0,0 +1,14 @@
+#ifndef GENERIC_LIB_H
+#define GENERIC_LIB_H
+
+enum class OptionA {
+  A,
+};
+
+enum class OptionB {
+  B,
+};
+
+template <class T> bool process(OptionA format, OptionB method);
+
+#endif // GENERIC_LIB_H

tests/hermeticity/main.cu

@@ -0,0 +1,6 @@
+#include "lib.h"
+
+int main() {
+  process<unsigned char>(OptionA::A, OptionB::B);
+  return 0;
+}

tests/hermeticity/test.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+NC='\033[0m'
+
+set -euo pipefail
+
+file=$(bazel info execution_root)/$(bazel cquery --output=files :cuda_test)
+
+bazel build :cuda_test
+build_output1=$(strings ${file})
+
+bazel clean
+
+bazel build :cuda_test
+build_output2=$(strings ${file})
+
+diff_output=$(diff -u <(echo "$build_output1") <(echo "$build_output2") --color=always || true)
+
+if [[ -n "$diff_output" ]]; then
+    echo -e "${RED}ERROR: Build outputs are not hermetic (differences detected):${NC}"
+    echo "$diff_output"
+    exit 1
+else
+    echo -e "${GREEN}SUCCESS: Build outputs are hermetic (no differences)${NC}"
+fi