Get rid of compiler warnings #392
Description
Our build system currently asks the compiler to print many useful warnings (-Wall). This sounds like a good idea since warnings may indicate problematic places in the code, obsolete features, or the use of nonstandard extension of C/C++. However, it appears that the reported warnings have been ignored for quite a long time. Currently there are about 3,000 warnings reported by gcc 4.8.5. A goal to address all the warnings should be recognized and a zero-warning policy should be enforced for all future code modifications.
A list of warnings sorted by their frequency in the build log (gcc 4.8.5, root 5):
msg count freq
0 deprecated conversion from string constant to [-Wwrite-strings] 798 27.0%
1 may be used uninitialized in this function [-Wmaybe-uninitialized] 435 14.7%
2 deleting object of polymorphic class type which has non-virtual de... 403 13.6%
3 variable set but not used [-Wunused-but-set-variable] 341 11.5%
4 unused variable [-Wunused-variable] 293 9.9%
5 format expects argument of type, but argument has type [-Wformat=] 210 7.1%
6 comparison between signed and unsigned integer expressions [-Wsign... 73 2.5%
7 iteration invokes undefined behavior [-Waggressive-loop-optimizati... 56 1.9%
8 operation on may be undefined [-Wsequence-point] 54 1.8%
9 declaration of shadows a member of [-Wshadow] 41 1.4%
10 converting to non-pointer type from NULL [-Wconversion-null] 30 1.0%
11 unused parameter [-Wunused-parameter] 25 0.8%
12 ignoring #pragma omp section [-Wunknown-pragmas] 22 0.7%
13 was hidden [-Woverloaded-virtual] 20 0.7%
14 array subscript is above array bounds [-Warray-bounds] 14 0.5%
15 dereferencing type-punned pointer will break strict-aliasing rules... 13 0.4%
16 defined but not used [-Wunused-variable] 12 0.4%
17 will be initialized after [-Wreorder] 11 0.4%
18 defined but not used [-Wunused-function] 9 0.3%
19 unknown conversion type character in format [-Wformat=] 8 0.3%
20 control reaches end of non-void function [-Wreturn-type] 7 0.2%
21 argument to in call is the same pointer type as the destination; e... 7 0.2%
22 too many arguments for format [-Wformat-extra-args] 7 0.2%
23 type qualifiers ignored on function return type [-Wignored-qualifi... 6 0.2%
24 value computed is not used [-Wunused-value] 6 0.2%
25 suggest explicit braces to avoid ambiguous [-Wparentheses] 6 0.2%
26 statement has no effect [-Wunused-value] 5 0.2%
27 within comment [-Wcomment] 5 0.2%
28 base class should be explicitly initialized in the copy constructo... 4 0.1%
29 comparison with string literal results in unspecified behaviour [-... 4 0.1%
30 cast to pointer from integer of different size [-Wint-to-pointer-c... 4 0.1%
31 suggest parentheses around within [-Wparentheses] 3 0.1%
32 the address of will always evaluate as [-Waddress] 3 0.1%
33 suggest parentheses around comparison in operand of [-Wparentheses] 3 0.1%
34 extra tokens at end of #endif directive [enabled by default] 2 0.1%
35 large integer implicitly truncated to unsigned type [-Woverflow] 2 0.1%
36 typedef locally defined but not used [-Wunused-local-typedefs] 2 0.1%
37 redefined [enabled by default] 2 0.1%
38 repeated flag in format [-Wformat=] 2 0.1%
39 argument to in call is the same expression as the destination; did... 2 0.1%
40 ignoring #pragma omp parallel [-Wunknown-pragmas] 2 0.1%
41 no return statement in function returning non-void [-Wreturn-type] 2 0.1%
42 use of length modifier with type character [-Wformat=] 1 0.0%
43 initialized and declared [enabled by default] 1 0.0%
44 field precision specifier expects argument of type, but argument h... 1 0.0%
45 zero-length gnu_printf format string [-Wformat-zero-length] 1 0.0%
46 format expects a matching argument [-Wformat=] 1 0.0%
47 label defined but not used [-Wunused-label] 1 0.0%
