[Sema] Enable -Wimplicit-float-conversion for integral to floating point precision loss

Issue an warning when the code tries to do an implicit int -> float
conversion, where the float type ha a narrower significant than the
float type.

The new warning is controlled by flag -Wimplicit-int-float-conversion,
under -Wimplicit-float-conversion and -Wconversion. It is also silenced
when c++11 narrowing warning is issued.

Differential Revision: https://reviews.llvm.org/D64666

llvm-svn: 367497

1 files changed, 53 insertions, 0 deletions

diff --git a/clang/test/Sema/implicit-int-float-conversion.c b/clang/test/Sema/implicit-int-float-conversion.c
new file mode 100644
index 00000000000..0933cd93516
--- /dev/null
+++ b/clang/test/Sema/implicit-int-float-conversion.c
@@ -0,0 +1,53 @@
+// RUN: %clang_cc1 %s -verify -Wno-conversion -Wimplicit-int-float-conversion
+
+long testReturn(long a, float b) {
+  return a + b; // expected-warning {{implicit conversion from 'long' to 'float' may lose precision}}
+}
+
+void testAssignment() {
+  float f = 222222;
+  double b = 222222222222L;
+
+#ifndef __ILP32__
+  float ff = 222222222222L;    // expected-warning {{implicit conversion from 'long' to 'float' changes value from 222222222222 to 222222221312}}
+  float ffff = 222222222222UL; // expected-warning {{implicit conversion from 'unsigned long' to 'float' changes value from 222222222222 to 222222221312}}
+#else
+  float ff = 222222222222L;    // expected-warning {{implicit conversion from 'long long' to 'float' changes value from 222222222222 to 222222221312}}
+  float ffff = 222222222222UL; // expected-warning {{implicit conversion from 'unsigned long long' to 'float' changes value from 222222222222 to 222222221312}}
+#endif
+
+  long l = 222222222222L;
+  float fff = l; // expected-warning {{implicit conversion from 'long' to 'float' may lose precision}}
+}
+
+void testExpression() {
+  float a = 0.0f;
+
+#ifndef __ILP32__
+  float b = 222222222222L + a; // expected-warning {{implicit conversion from 'long' to 'float' changes value from 222222222222 to 222222221312}}
+#else
+  float b = 222222222222L + a; // expected-warning {{implicit conversion from 'long long' to 'float' changes value from 222222222222 to 222222221312}}
+#endif
+
+  float g = 22222222 + 22222222;
+  float c = 22222222 + 22222223; // expected-warning {{implicit conversion from 'int' to 'float' changes value from 44444445 to 44444444}}
+
+  int i = 0;
+  float d = i + a; // expected-warning {{implicit conversion from 'int' to 'float' may lose precision}}
+
+  double e = 0.0;
+  double f = i + e;
+}
+
+void testCNarrowing() {
+  // Since this is a C file. C++11 narrowing is not in effect.
+  // In this case, we should issue warnings.
+#ifndef __ILP32__
+  float a = {222222222222L}; // expected-warning {{implicit conversion from 'long' to 'float' changes value from 222222222222 to 222222221312}}
+#else
+  float a = {222222222222L};   // expected-warning {{implicit conversion from 'long long' to 'float' changes value from 222222222222 to 222222221312}}
+#endif
+
+  long b = 222222222222L;
+  float c = {b}; // expected-warning {{implicit conversion from 'long' to 'float' may lose precision}}
+}