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gsl_assert changes: (#452)

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* GSL_LIKELY/_UNLIKELY always contextually convert their argument to bool.

* Add macro GSL_ASSUME(cond) to inform the optimizer that the predicate cond must hold.

* Reimplement Expects & Ensures as expressions for flexibility and correctness. (Think about "if (cond1) Expects(cond2); else goto fail;")

* Expects and Ensures GSL_ASSUME their predicate when GSL_UNENFORCED_ON_CONTRACT_VIOLATION is defined.
This commit is contained in:
Casey Carter 2017-03-20 09:30:14 -07:00 committed by Neil MacIntosh
parent 5905d2d774
commit 16a6a41690
1 changed files with 31 additions and 19 deletions
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50
include/gsl/gsl_assert
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@ -30,20 +30,36 @@
// 2. GSL_THROW_ON_CONTRACT_VIOLATION: a gsl::fail_fast exception will be thrown
// 3. GSL_UNENFORCED_ON_CONTRACT_VIOLATION: nothing happens
//
#if !(defined(GSL_THROW_ON_CONTRACT_VIOLATION) || defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION) || \
#if !(defined(GSL_THROW_ON_CONTRACT_VIOLATION) || defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION) || \
defined(GSL_UNENFORCED_ON_CONTRACT_VIOLATION))
#define GSL_TERMINATE_ON_CONTRACT_VIOLATION
#define GSL_TERMINATE_ON_CONTRACT_VIOLATION
#endif
#define GSL_STRINGIFY_DETAIL(x) #x
#define GSL_STRINGIFY(x) GSL_STRINGIFY_DETAIL(x)
#if defined(__clang__) || defined(__GNUC__)
#define GSL_LIKELY(x) __builtin_expect (!!(x), 1)
#define GSL_UNLIKELY(x) __builtin_expect (!!(x), 0)
#define GSL_LIKELY(x) __builtin_expect (!!(x), 1)
#define GSL_UNLIKELY(x) __builtin_expect (!!(x), 0)
#else
#define GSL_LIKELY(x) (x)
#define GSL_UNLIKELY(x) (x)
#define GSL_LIKELY(x) (!!(x))
#define GSL_UNLIKELY(x) (!!(x))
#endif
//
// GSL_ASSUME(cond)
//
// Tell the optimizer that the predicate cond must hold. It is unspecified
// whether or not cond is actually evaluated.
//
#ifdef _MSC_VER
#define GSL_ASSUME(cond) __assume(cond)
#elif defined(__clang__)
#define GSL_ASSUME(cond) __builtin_assume(cond)
#elif defined(__GNUC__)
#define GSL_ASSUME(cond) ((cond) ? static_cast<void>(0) : __builtin_unreachable())
#else
#define GSL_ASSUME(cond) static_cast<void>(!!(cond))
#endif
//
@ -60,26 +76,22 @@ struct fail_fast : public std::runtime_error
#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
#define Expects(cond) \
if (GSL_UNLIKELY(!(cond))) \
throw gsl::fail_fast("GSL: Precondition failure at " __FILE__ ": " GSL_STRINGIFY(__LINE__));
#define Ensures(cond) \
if (GSL_UNLIKELY(!(cond))) \
throw gsl::fail_fast("GSL: Postcondition failure at " __FILE__ \
": " GSL_STRINGIFY(__LINE__));
#define GSL_CONTRACT_CHECK(type, cond) \
(GSL_LIKELY(cond) ? static_cast<void>(0) : \
throw gsl::fail_fast("GSL: " type " failure at " __FILE__ ": " GSL_STRINGIFY(__LINE__)))
#elif defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION)
#define Expects(cond) \
if (GSL_UNLIKELY(!(cond))) std::terminate();
#define Ensures(cond) \
if (GSL_UNLIKELY(!(cond))) std::terminate();
#define GSL_CONTRACT_CHECK(type, cond) \
(GSL_LIKELY(cond) ? static_cast<void>(0) : std::terminate())
#elif defined(GSL_UNENFORCED_ON_CONTRACT_VIOLATION)
#define Expects(cond)
#define Ensures(cond)
#define GSL_CONTRACT_CHECK(type, cond) GSL_ASSUME(cond)
#endif
#define Expects(cond) GSL_CONTRACT_CHECK("Precondition", cond)
#define Ensures(cond) GSL_CONTRACT_CHECK("Postcondition", cond)
#endif // GSL_CONTRACTS_H