src/utils/warning_nocompile.nc

// Copyright 2026 The Dawn & Tint Authors
//
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// Tests for warnings. Note this code should ONLY trigger warnings (no other hard errors),
// otherwise the compiler suppresses the warnings in favor of the errors.

#include <stdint.h>

#include <array>
#include <span>

#include "src/utils/heap_array.h"
#include "src/utils/span.h"

namespace dawn {

// Verify that warnings that are part of -Weverything but not -Wall -Wextra
// are enabled. This test runs only when `dawn_weverything = true`.
void TestWeverything() {
    // -Wzero-as-null-pointer-constant is one such warning.
    [[maybe_unused]] void* p = 0; // expected-error {{zero as null pointer constant}}
}

// Verify that warnings suppressions limited to specific file with --warning-suppression-mappings
// are enabled to other code.
void TestWarningSuppressionMappings() {
    // -Wold-style-cast is one such warning.
    int x = 0;
    [[maybe_unused]] float y = (float)x; // expected-error {{use of old-style cast}}
}

// -Wunsafe-buffer-usage: operator[] on T*
void TestUnsafeBuffersRawPointer() {
    constexpr std::array<int, 4> arr{};

    // Safe to get a pointer to the first element.
    const int* arrPtr = arr.data();

    // But unsafe to use it like an array.
    { [[maybe_unused]] int x = arr[1]; }
    { [[maybe_unused]] int x = std::span(arr)[1]; }
    { [[maybe_unused]] int x = arrPtr[1]; }  // expected-error {{unsafe buffer access}}
}

// -Wunsafe-buffer-usage-in-libc-call: memcpy()
// This is skipped on Android because with Android Bionic's _FORTIFY_SOURCE,
// memcpy is a static inline wrapper (__BIONIC_FORTIFY_INLINE). This causes
// Clang's unsafe-buffer-usage checker to ignore it (as it only matches global
// functions or std:: functions), which then causes the expected error to not
// be raised.
#if !defined(__ANDROID__)
void TestUnsafeBuffersMemcpy() {
    int x = 1;
    int y = 2;
    memcpy(&y, &x, sizeof(int));  // expected-error {{function 'memcpy' is unsafe}}
}
#endif  // !defined(__ANDROID__)

// -Wunsafe-buffer-usage: std::span() constructors
void TestUnsafeBuffersStdSpanConstructors() {
    std::array<int, 4> arr{};
    // std::span is NOT tagged as being unsafe when using the unsafe buffers plugin.
    // (If we use -Wunsafe-buffer-usage without the plugin, it would be. This may be fixable.)
    { [[maybe_unused]] auto s = std::span(arr.data(), arr.size()); }
    { [[maybe_unused]] std::span<int> s(arr.data(), arr.size()); }
}

// -Wunsafe-buffer-usage: dawn::Span() constructors
void TestUnsafeBuffersDawnSpanConstructors() {
    {
        constexpr std::array<int, 5> kArr{};

        DAWN_UNSAFE_BUFFERS(Span<const int>(kArr.data(), kArr.size()));  // Control case.
        Span<const int>(kArr.data(), kArr.size());  // expected-error {{introduces unsafe buffer manipulation}}

        DAWN_UNSAFE_BUFFERS(Span<const int>(kArr.begin(), kArr.end()));  // Control case.
        Span<const int>(kArr.begin(), kArr.end());  // expected-error {{introduces unsafe buffer manipulation}}
    }
}

// -Wunsafe-buffer-usage: dawn::HeapArray::Uninit()
void TestUnsafeBuffersDawnHeapArrayConstructors() {
    { [[maybe_unused]] auto x = DAWN_UNSAFE_BUFFERS(HeapArray<int>::Uninit(4)); }  // Control case.
    { [[maybe_unused]] auto x = HeapArray<int>::Uninit(4); }  // expected-error {{introduces unsafe buffer manipulation}}

    { [[maybe_unused]] auto x = DAWN_UNSAFE_BUFFERS(HeapArray<int>::Uninit(4, std::nothrow)); }  // Control case.
    { [[maybe_unused]] auto x = HeapArray<int>::Uninit(4, std::nothrow); }  // expected-error {{introduces unsafe buffer manipulation}}
}

}