clang/test/Sema/tautological-unsigned-enum-zero-compare.cpp

   1 // RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-linux-gnu -fsyntax-only \
   2 // RUN:            -Wtautological-unsigned-enum-zero-compare \
   3 // RUN:            -verify=unsigned,unsigned-signed %s
   4 // RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-win32 -fsyntax-only \
   5 // RUN:            -Wtautological-unsigned-enum-zero-compare \
   6 // RUN:            -verify=unsigned-signed %s
   7 // RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-win32 -fsyntax-only \
   8 // RUN:            -verify=silence %s
   9
  10 // silence-no-diagnostics
  11
  12 int main() {
  13   // On Windows, all enumerations have a fixed underlying type, which is 'int'
  14   // if not otherwise specified, so A is identical to C on Windows. Otherwise,
  15   // we follow the C++ rules, which say that the only valid values of A are 0
  16   // and 1.
  17   enum A { A_foo = 0, A_bar, };
  18   enum A a;
  19
  20   enum B : unsigned { B_foo = 0, B_bar, };
  21   enum B b;
  22
  23   enum C : signed { C_foo = 0, C_bar, };
  24   enum C c;
  25
  26   if (a < 0) // unsigned-warning {{comparison of unsigned enum expression < 0 is always false}}
  27     return 0;
  28   if (0 >= a)
  29     return 0;
  30   if (a > 0)
  31     return 0;
  32   if (0 <= a) // unsigned-warning {{comparison of 0 <= unsigned enum expression is always true}}
  33     return 0;
  34   if (a <= 0)
  35     return 0;
  36   if (0 > a) // unsigned-warning {{comparison of 0 > unsigned enum expression is always false}}
  37     return 0;
  38   if (a >= 0) // unsigned-warning {{comparison of unsigned enum expression >= 0 is always true}}
  39     return 0;
  40   if (0 < a)
  41     return 0;
  42
  43   // FIXME: As below, the issue here is that the enumeration is promoted to
  44   // unsigned.
  45   if (a < 0U) // unsigned-signed-warning {{comparison of unsigned enum expression < 0 is always false}}
  46     return 0;
  47   if (0U >= a)
  48     return 0;
  49   if (a > 0U)
  50     return 0;
  51   if (0U <= a) // unsigned-signed-warning {{comparison of 0 <= unsigned enum expression is always true}}
  52     return 0;
  53   if (a <= 0U)
  54     return 0;
  55   if (0U > a) // unsigned-signed-warning {{comparison of 0 > unsigned enum expression is always false}}
  56     return 0;
  57   if (a >= 0U) // unsigned-signed-warning {{comparison of unsigned enum expression >= 0 is always true}}
  58     return 0;
  59   if (0U < a)
  60     return 0;
  61
  62   if (b < 0) // unsigned-signed-warning {{comparison of unsigned enum expression < 0 is always false}}
  63     return 0;
  64   if (0 >= b)
  65     return 0;
  66   if (b > 0)
  67     return 0;
  68   if (0 <= b) // unsigned-signed-warning {{comparison of 0 <= unsigned enum expression is always true}}
  69     return 0;
  70   if (b <= 0)
  71     return 0;
  72   if (0 > b) // unsigned-signed-warning {{comparison of 0 > unsigned enum expression is always false}}
  73     return 0;
  74   if (b >= 0) // unsigned-signed-warning {{comparison of unsigned enum expression >= 0 is always true}}
  75     return 0;
  76   if (0 < b)
  77     return 0;
  78
  79   if (b < 0U) // unsigned-signed-warning {{comparison of unsigned enum expression < 0 is always false}}
  80     return 0;
  81   if (0U >= b)
  82     return 0;
  83   if (b > 0U)
  84     return 0;
  85   if (0U <= b) // unsigned-signed-warning {{comparison of 0 <= unsigned enum expression is always true}}
  86     return 0;
  87   if (b <= 0U)
  88     return 0;
  89   if (0U > b) // unsigned-signed-warning {{comparison of 0 > unsigned enum expression is always false}}
  90     return 0;
  91   if (b >= 0U) // unsigned-signed-warning {{comparison of unsigned enum expression >= 0 is always true}}
  92     return 0;
  93   if (0U < b)
  94     return 0;
  95
  96   if (c < 0)
  97     return 0;
  98   if (0 >= c)
  99     return 0;
 100   if (c > 0)
 101     return 0;
 102   if (0 <= c)
 103     return 0;
 104   if (c <= 0)
 105     return 0;
 106   if (0 > c)
 107     return 0;
 108   if (c >= 0)
 109     return 0;
 110   if (0 < c)
 111     return 0;
 112
 113   // FIXME: These diagnostics are terrible. The issue here is that the signed
 114   // enumeration value was promoted to an unsigned type.
 115   if (c < 0U) // unsigned-signed-warning {{comparison of unsigned enum expression < 0 is always false}}
 116     return 0;
 117   if (0U >= c)
 118     return 0;
 119   if (c > 0U)
 120     return 0;
 121   if (0U <= c) // unsigned-signed-warning {{comparison of 0 <= unsigned enum expression is always true}}
 122     return 0;
 123   if (c <= 0U)
 124     return 0;
 125   if (0U > c) // unsigned-signed-warning {{comparison of 0 > unsigned enum expression is always false}}
 126     return 0;
 127   if (c >= 0U) // unsigned-signed-warning {{comparison of unsigned enum expression >= 0 is always true}}
 128     return 0;
 129   if (0U < c)
 130     return 0;
 131
 132   return 1;
 133 }
 134
 135 namespace crash_enum_zero_width {
 136 int test() {
 137   enum A : unsigned {
 138     A_foo = 0
 139   };
 140   enum A a;
 141
 142   // used to crash in llvm::APSInt::getMaxValue()
 143   if (a < 0) // unsigned-signed-warning {{comparison of unsigned enum expression < 0 is always false}}
 144     return 0;
 145
 146   return 1;
 147 }
 148 } // namespace crash_enum_zero_width