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Add builtin_unreachable to the FW_ASSERT macros #5228

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Add builtin_unreachable to the FW_ASSERT macros #5228

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d04aae0
Update Assert.hpp
garthwatney Jun 2, 2026
2ec0abb
Add FW_UNREACHABLE macro for better compatibility
thomas-bc Jun 2, 2026
469d891
Refactor FW_ASSERT_UNREACHABLE macro definition
thomas-bc Jun 12, 2026
f293c95
Refactor FW_UNREACHABLE definition for better compatibility
thomas-bc Jun 12, 2026
1468516
Guard ifndef
thomas-bc Jun 12, 2026
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54 changes: 43 additions & 11 deletions Fw/Types/Assert.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,35 @@
// Return all the arguments of the macro, but the first one
#define FW_ASSERT_NO_FIRST_ARG(ARG_0, ...) __VA_ARGS__

// Define FW_UNREACHABLE to hint to the compiler that a code path is unreachable.
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thomas-bc marked this conversation as resolved.
// Falls back to a no-op on compilers that do not support __builtin_unreachable.
// (1) __has_builtin — the modern check, available in Clang and GCC >= 10.
// (2) defined(__GNUC__) — catches older GCC (4.5–9) which lack __has_builtin
#ifndef FW_UNREACHABLE
#ifdef __has_builtin
#if __has_builtin(__builtin_unreachable)
#define FW_UNREACHABLE() __builtin_unreachable()
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#endif
#endif
Comment on lines +11 to +19

@lestarch-autobot lestarch-autobot Jun 12, 2026

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The Copilot review correctly identified that this branch can redefine a user-provided FW_UNREACHABLE. Other macros in this file (e.g., FW_ASSERT_NORETURN at line 88, NOINLINE at line 102) use #ifndef guards. Wrapping the __has_builtin detection in #ifndef FW_UNREACHABLE prevents redefinition warnings and allows intentional overrides.

Suggested change
// Define FW_UNREACHABLE to hint to the compiler that a code path is unreachable.
// Falls back to a no-op on compilers that do not support __builtin_unreachable.
// (1) __has_builtin — the modern check, available in Clang and GCC >= 10.
// (2) defined(__GNUC__) — catches older GCC (4.5–9) which lack __has_builtin
#ifdef __has_builtin
#if __has_builtin(__builtin_unreachable)
#define FW_UNREACHABLE() __builtin_unreachable()
#endif
#endif
// Define FW_UNREACHABLE to hint to the compiler that a code path is unreachable.
// Users may pre-define FW_UNREACHABLE to override the detection below.
// Falls back to a no-op on compilers that do not support __builtin_unreachable.
// (1) __has_builtin — the modern check, available in Clang and GCC >= 10.
// (2) defined(__GNUC__) — catches older GCC (4.5–9) which lack __has_builtin
#ifndef FW_UNREACHABLE
#ifdef __has_builtin
#if __has_builtin(__builtin_unreachable)
#define FW_UNREACHABLE() __builtin_unreachable()
#endif
#endif
#endif

#endif
#ifndef FW_UNREACHABLE
#if defined(__GNUC__)
#define FW_UNREACHABLE() __builtin_unreachable()
#else
#define FW_UNREACHABLE() ((void)0) // no-op fallback for unknown compilers
#endif
#endif

// FW_ASSERT_UNREACHABLE is the hint used inside FW_ASSERT macros.
// Only active when FW_ASSERTIONS_ALWAYS_ABORT is enabled, because SwAssert
// can legally return when it is disabled (the default). Using __builtin_unreachable
// after a call that returns is undefined behavior.
#if FW_ASSERTIONS_ALWAYS_ABORT
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#define FW_ASSERT_UNREACHABLE() FW_UNREACHABLE()
#else
#define FW_ASSERT_UNREACHABLE() ((void)0)
#endif

#if FW_ASSERT_LEVEL == FW_NO_ASSERT
// Users may override the NO_ASSERT case should they choose
#ifndef FW_ASSERT
Expand All @@ -23,24 +52,27 @@
#define FW_ASSERT(...) \
((FW_ASSERT_FIRST_ARG(__VA_ARGS__, 0)) \
? ((void)0) \
: (Fw::SwAssert(ASSERT_FILE_ID, FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__))))
: (Fw::SwAssert(ASSERT_FILE_ID, FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__)), FW_ASSERT_UNREACHABLE()))
#elif FW_ASSERT_LEVEL == FW_FILEID_ASSERT && !defined ASSERT_FILE_ID
#define FILE_NAME_ARG U32
#define FW_ASSERT(...) \
((FW_ASSERT_FIRST_ARG(__VA_ARGS__, 0)) \
? ((void)0) \
: (Fw::SwAssert(static_cast<U32>(0), FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__))))
#define FW_ASSERT(...) \
((FW_ASSERT_FIRST_ARG(__VA_ARGS__, 0)) \
? ((void)0) \
: (Fw::SwAssert(static_cast<U32>(0), FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__)), \
FW_ASSERT_UNREACHABLE()))
#elif FW_ASSERT_LEVEL == FW_RELATIVE_PATH_ASSERT && defined ASSERT_RELATIVE_PATH
#define FILE_NAME_ARG const CHAR*
#define FW_ASSERT(...) \
((FW_ASSERT_FIRST_ARG(__VA_ARGS__, 0)) \
? ((void)0) \
: (Fw::SwAssert(ASSERT_RELATIVE_PATH, FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__)), \
FW_ASSERT_UNREACHABLE()))
#else
#define FILE_NAME_ARG const CHAR*
#define FW_ASSERT(...) \
((FW_ASSERT_FIRST_ARG(__VA_ARGS__, 0)) \
? ((void)0) \
: (Fw::SwAssert(ASSERT_RELATIVE_PATH, FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__))))
#else
#define FILE_NAME_ARG const CHAR*
#define FW_ASSERT(...) \
((FW_ASSERT_FIRST_ARG(__VA_ARGS__, 0)) ? ((void)0) \
: (Fw::SwAssert(__FILE__, FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__))))
: (Fw::SwAssert(__FILE__, FW_ASSERT_NO_FIRST_ARG(__VA_ARGS__, __LINE__)), FW_ASSERT_UNREACHABLE()))
#endif
#endif // if ASSERT is defined

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