Support `-fno-exceptions`. am: 2df0091468 am: 5fb579c6c1 am: 3923d3e94fandroid-wear-8.1.0_r1android-vts-8.1_r9android-vts-8.1_r8android-vts-8.1_r7android-vts-8.1_r6android-vts-8.1_r5android-vts-8.1_r4android-vts-8.1_r3android-vts-8.1_r14android-vts-8.1_r13android-vts-8.1_r12android-vts-8.1_r11android-vts-8.1_r10android-vts-8.0_r9android-vts-8.0_r8android-vts-8.0_r7android-vts-8.0_r6android-vts-8.0_r2android-vts-8.0_r13android-vts-8.0_r12android-vts-8.0_r11android-vts-8.0_r10android-vts-8.0_r1android-security-8.1.0_r93android-security-8.1.0_r92android-security-8.1.0_r91android-security-8.1.0_r90android-security-8.1.0_r89android-security-8.1.0_r88android-security-8.1.0_r87android-security-8.1.0_r86android-security-8.1.0_r85android-security-8.1.0_r84android-security-8.1.0_r83android-security-8.1.0_r82android-security-8.0.0_r54android-security-8.0.0_r53android-security-8.0.0_r52android-cts-8.1_r9android-cts-8.1_r8android-cts-8.1_r7android-cts-8.1_r6android-cts-8.1_r5android-cts-8.1_r4android-cts-8.1_r3android-cts-8.1_r25android-cts-8.1_r24android-cts-8.1_r23android-cts-8.1_r22android-cts-8.1_r21android-cts-8.1_r20android-cts-8.1_r2android-cts-8.1_r19android-cts-8.1_r18android-cts-8.1_r17android-cts-8.1_r16android-cts-8.1_r15android-cts-8.1_r14android-cts-8.1_r13android-cts-8.1_r12android-cts-8.1_r11android-cts-8.1_r10android-cts-8.1_r1android-cts-8.0_r9android-cts-8.0_r8android-cts-8.0_r7android-cts-8.0_r6android-cts-8.0_r5android-cts-8.0_r4android-cts-8.0_r3android-cts-8.0_r26android-cts-8.0_r25android-cts-8.0_r24android-cts-8.0_r23android-cts-8.0_r22android-cts-8.0_r21android-cts-8.0_r20android-cts-8.0_r2android-cts-8.0_r19android-cts-8.0_r18android-cts-8.0_r17android-cts-8.0_r16android-cts-8.0_r15android-cts-8.0_r14android-cts-8.0_r13android-cts-8.0_r12android-cts-8.0_r11android-cts-8.0_r10android-cts-8.0_r1android-cts-7.1_r18android-8.1.0_r9android-8.1.0_r81android-8.1.0_r80android-8.1.0_r8android-8.1.0_r79android-8.1.0_r78android-8.1.0_r77android-8.1.0_r76android-8.1.0_r75android-8.1.0_r74android-8.1.0_r73android-8.1.0_r72android-8.1.0_r71android-8.1.0_r70android-8.1.0_r7android-8.1.0_r69android-8.1.0_r68android-8.1.0_r67android-8.1.0_r66android-8.1.0_r65android-8.1.0_r64android-8.1.0_r63android-8.1.0_r62android-8.1.0_r61android-8.1.0_r60android-8.1.0_r6android-8.1.0_r53android-8.1.0_r52android-8.1.0_r51android-8.1.0_r50android-8.1.0_r5android-8.1.0_r48android-8.1.0_r47android-8.1.0_r46android-8.1.0_r45android-8.1.0_r43android-8.1.0_r42android-8.1.0_r41android-8.1.0_r40android-8.1.0_r4android-8.1.0_r39android-8.1.0_r38android-8.1.0_r37android-8.1.0_r36android-8.1.0_r35android-8.1.0_r33android-8.1.0_r32android-8.1.0_r31android-8.1.0_r30android-8.1.0_r3android-8.1.0_r29android-8.1.0_r28android-8.1.0_r27android-8.1.0_r26android-8.1.0_r25android-8.1.0_r23android-8.1.0_r22android-8.1.0_r21android-8.1.0_r20android-8.1.0_r2android-8.1.0_r19android-8.1.0_r18android-8.1.0_r17android-8.1.0_r16android-8.1.0_r15android-8.1.0_r14android-8.1.0_r13android-8.1.0_r12android-8.1.0_r11android-8.1.0_r10android-8.1.0_r1android-8.0.0_r9android-8.0.0_r7android-8.0.0_r51android-8.0.0_r50android-8.0.0_r49android-8.0.0_r48android-8.0.0_r47android-8.0.0_r46android-8.0.0_r45android-8.0.0_r44android-8.0.0_r43android-8.0.0_r42android-8.0.0_r41android-8.0.0_r40android-8.0.0_r4android-8.0.0_r39android-8.0.0_r38android-8.0.0_r37android-8.0.0_r36android-8.0.0_r35android-8.0.0_r34android-8.0.0_r33android-8.0.0_r32android-8.0.0_r31android-8.0.0_r30android-8.0.0_r3android-8.0.0_r29android-8.0.0_r28android-8.0.0_r27android-8.0.0_r26android-8.0.0_r25android-8.0.0_r24android-8.0.0_r23android-8.0.0_r22android-8.0.0_r21android-8.0.0_r2android-8.0.0_r17android-8.0.0_r16android-8.0.0_r15android-8.0.0_r13android-8.0.0_r12android-8.0.0_r11android-8.0.0_r10android-8.0.0_r1security-oc-releasesecurity-oc-mr1-releaseoreo-vts-releaseoreo-security-releaseoreo-releaseoreo-r6-releaseoreo-r5-releaseoreo-r4-releaseoreo-r3-releaseoreo-r2-releaseoreo-mr1-wear-releaseoreo-mr1-vts-releaseoreo-mr1-security-releaseoreo-mr1-s1-releaseoreo-mr1-releaseoreo-mr1-devoreo-mr1-cuttlefish-testingoreo-mr1-cts-releaseoreo-m8-releaseoreo-m7-releaseoreo-m6-s4-releaseoreo-m6-s3-releaseoreo-m6-s2-releaseoreo-m5-releaseoreo-m4-s9-releaseoreo-m4-s8-releaseoreo-m4-s7-releaseoreo-m4-s6-releaseoreo-m4-s5-releaseoreo-m4-s4-releaseoreo-m4-s3-releaseoreo-m4-s2-releaseoreo-m4-s12-releaseoreo-m4-s11-releaseoreo-m4-s10-releaseoreo-m4-s1-releaseoreo-m3-releaseoreo-m2-s5-releaseoreo-m2-s4-releaseoreo-m2-s3-releaseoreo-m2-s2-releaseoreo-m2-s1-releaseoreo-m2-releaseoreo-dr3-releaseoreo-dr2-releaseoreo-dr1-releaseoreo-dr1-devoreo-devoreo-cts-release

am: 44079759f9

Change-Id: Ia42174d411ba16565d583020d793d01ba47a462e

1 files changed, 28 insertions, 11 deletions

diff --git a/gsl/gsl_util b/gsl/gsl_util
index f0ac964..a8a41ae 100644
--- a/gsl/gsl_util
+++ b/gsl/gsl_util
@@ -48,6 +48,18 @@
 
 #endif // _MSC_VER
 
+// AFAIK there's no way to detect in GCC or MSVC. GCC has an __EXCEPTIONS macro,
+// but that is only defined if `-fexceptions` is *explicitly* passed on the
+// command line; defaulting to exceptions enabled will not set this macro.
+//
+// Non-Clang users will need to defined GSL_NO_EXCEPTIONS explicitly from the
+// command line if they are building with exceptions disabled.
+#if defined(__clang__) && !__has_feature(cxx_exceptions)
+// If building with -fno-exceptions, we'll fall back to gsl::Ensures in places
+// where we would have normally thrown an exception.
+#define GSL_NO_EXCEPTIONS
+#endif // defined(__has_feature) && !__has_feature(cxx_exceptions)
+
 namespace gsl
 {
 //
@@ -125,9 +137,14 @@ template <class T, class U>
 inline T narrow(U u)
 {
     T t = narrow_cast<T>(u);
+#ifndef GSL_NO_EXCEPTIONS
     if (static_cast<U>(t) != u) throw narrowing_error();
     if (!details::is_same_signedness<T, U>::value && ((t < T{}) != (u < U{})))
         throw narrowing_error();
+#else
+    Ensures(static_cast<U>(t) == u);
+    Ensures(!(!details::is_same_signedness<T, U>::value && ((t < T{}) != (u < U{}))));
+#endif
     return t;
 }
 
@@ -135,30 +152,30 @@ inline T narrow(U u)
 // at() - Bounds-checked way of accessing static arrays, std::array, std::vector
 //
 template <class T, size_t N>
-constexpr T& at(T (&arr)[N], size_t index)
+constexpr T& at(T (&arr)[N], std::ptrdiff_t index)
 {
-    Expects(index < N);
-    return arr[index];
+    Expects(index >= 0 && index < narrow_cast<std::ptrdiff_t>(N));
+    return arr[static_cast<size_t>(index)];
 }
 
 template <class T, size_t N>
-constexpr T& at(std::array<T, N>& arr, size_t index)
+constexpr T& at(std::array<T, N>& arr, std::ptrdiff_t index)
 {
-    Expects(index < N);
-    return arr[index];
+    Expects(index >= 0 && index < narrow_cast<std::ptrdiff_t>(N));
+    return arr[static_cast<size_t>(index)];
 }
 
 template <class Cont>
-constexpr typename Cont::value_type& at(Cont& cont, size_t index)
+constexpr typename Cont::value_type& at(Cont& cont, std::ptrdiff_t index)
 {
-    Expects(index < cont.size());
-    return cont[index];
+    Expects(index >= 0 && index < narrow_cast<std::ptrdiff_t>(cont.size()));
+    return cont[static_cast<typename Cont::size_type>(index)];
 }
 
 template <class T>
-constexpr const T& at(std::initializer_list<T> cont, size_t index)
+constexpr const T& at(std::initializer_list<T> cont, std::ptrdiff_t index)
 {
-    Expects(index < cont.size());
+    Expects(index >= 0 && index < narrow_cast<std::ptrdiff_t>(cont.size()));
     return *(cont.begin() + index);
 }