[compiler-rt][NFC] Avoid implicit-integer-sign-change in FuzzedDataProvider::ConsumeI...

This makes the implicit conversion that is happening explicit.
Otherwise, each user is forced to suppress this
implicit-integer-sign-change runtime error in their their UBSAN
suppressions file.

For example, the runtime error might look like:

runtime error: implicit conversion from type 'long' of value -9223372036854775808 (64-bit, signed) to type 'uint64_t' (aka 'unsigned long') changed the value to 9223372036854775808 (64-bit, unsigned)
    #0 0x55fe29dea91d in long FuzzedDataProvider::ConsumeIntegralInRange<long>(long, long) src/./test/fuzz/FuzzedDataProvider.h:233:25
    [...]
SUMMARY: UndefinedBehaviorSanitizer: implicit-integer-sign-change test/fuzz/FuzzedDataProvider.h:233:25 in

Differential Revision: https://reviews.llvm.org/D155206

diff --git a/compiler-rt/include/fuzzer/FuzzedDataProvider.h b/compiler-rt/include/fuzzer/FuzzedDataProvider.h
index 71cb427..8a8214b 100644 (file)
--- a/compiler-rt/include/fuzzer/FuzzedDataProvider.h
+++ b/compiler-rt/include/fuzzer/FuzzedDataProvider.h
@@ -209,7 +209,7 @@ T FuzzedDataProvider::ConsumeIntegralInRange(T min, T max) {
     abort();
 
   // Use the biggest type possible to hold the range and the result.
-  uint64_t range = static_cast<uint64_t>(max) - min;
+  uint64_t range = static_cast<uint64_t>(max) - static_cast<uint64_t>(min);
   uint64_t result = 0;
   size_t offset = 0;
 
@@ -230,7 +230,7 @@ T FuzzedDataProvider::ConsumeIntegralInRange(T min, T max) {
   if (range != std::numeric_limits<decltype(range)>::max())
     result = result % (range + 1);
 
-  return static_cast<T>(min + result);
+  return static_cast<T>(static_cast<uint64_t>(min) + result);
 }
 
 // Returns a floating point value in the range [Type's lowest, Type's max] by