http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55643
Bug #: 55643
Summary: g++ 4.7 gives "warning: variable ‘myVar’ set but not
used [-Wunused-but-set-variable]" when an "enum
class"-typed variable is cast to double before use
Classification: Unclassified
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: [email protected]
ReportedBy: [email protected]
When I compile the attached C++ source file with g++ 4.7.2, I get this build
warning:
> gcc-warning-test.cpp: In function ‘int main()’:
> gcc-warning-test.cpp:19:10: warning: variable ‘myVar’ set but
> not used [-Wunused-but-set-variable]
I believe this is incorrect, because I _am_ using the variable -- I'm printing
out its value like so:
> printf("%f\n", (double)myVar);
If I instead cast it to an int or an unsigned value, I get no warning -- that
apparently counts as "using" it, from GCC's perspective. But when I use
(float)myVar or (double)myVar, GCC apparently doesn't count that as "using".
NOTE: This only happens with "enum class" (a C++11 feature). If I instead just
use "enum", then I don't get a warning.
For comparison, clang yields expected results. (No warning -- and it does warn
if I remove the printf statements, indicating that it is doing some checking)
SYSTEM INFO:
g++-4.7.real (Ubuntu/Linaro 4.7.2-2ubuntu1) 4.7.2
OS: Ubuntu 12.10
Kernel: Linux 3.5.0-19-generic x86_64
