[clang-tidy] Improving narrowing conversions

Summary:
Newly flagged narrowing conversions:
 - integer to narrower signed integer (this is compiler implementation defined),
 - integer - floating point narrowing conversions,
 - floating point - integer narrowing conversions,
 - constants with narrowing conversions (even in ternary operator).

Reviewers: hokein, alexfh, aaron.ballman, JonasToth

Reviewed By: aaron.ballman, JonasToth

Subscribers: lebedev.ri, courbet, nemanjai, xazax.hun, kbarton, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D53488

llvm-svn: 347570

1 files changed, 23 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/cppcoreguidelines-narrowing-conversions-long-is-32bits.cpp b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-narrowing-conversions-long-is-32bits.cpp
new file mode 100644
index 00000000000..dcf1848a30f
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-narrowing-conversions-long-is-32bits.cpp
@@ -0,0 +1,23 @@
+// RUN: %check_clang_tidy %s cppcoreguidelines-narrowing-conversions %t \
+// RUN: -- -- -target x86_64-unknown-linux -m32
+
+static_assert(sizeof(int) * 8 == 32, "int is 32-bits");
+static_assert(sizeof(long) * 8 == 32, "long is 32-bits");
+static_assert(sizeof(long long) * 8 == 64, "long long is 64-bits");
+
+void narrow_integer_to_signed_integer_is_not_ok() {
+  int i;        // i.e. int32_t
+  long l;       // i.e. int32_t
+  long long ll; // i.e. int64_t
+
+  unsigned int ui;        // i.e. uint32_t
+  unsigned long ul;       // i.e. uint32_t
+  unsigned long long ull; // i.e. uint64_t
+
+  i = l;  // int and long are the same type.
+  i = ll; // int64_t does not fit in an int32_t
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: narrowing conversion from 'long long' to signed type 'int' is implementation-defined [cppcoreguidelines-narrowing-conversions]
+  ll = ul;  // uint32_t fits into int64_t
+  ll = ull; // uint64_t does not fit in an int64_t
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: narrowing conversion from 'unsigned long long' to signed type 'long long' is implementation-defined [cppcoreguidelines-narrowing-conversions]
+}