Red Hat ENTERPRISE LINUX 4 Manual page 52

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-Wredundant-decls
Warn if anything is declared more than once in the same scope, even in cases where multiple
declaration is valid and changes nothing.
-Wnested-externs (C only)
Warn if an
extern
-Wunreachable-code
Warn if the compiler detects that code will never be executed.
This option is intended to warn when the compiler detects that at least a whole line of source
code will never be executed, because some condition is never satisfied or because it is after a
procedure that never returns.
It is possible for this option to produce a warning even though there are circumstances un-
der which part of the affected line can be executed, so care should be taken when removing
apparently-unreachable code.
For instance, when a function is inlined, a warning may mean that the line is unreachable in only
one inlined copy of the function.
This option is not made part of
substantial code which checks correct functioning of the program and is, hopefully, unreachable
because the program does work. Another common use of unreachable code is to provide behavior
which is selectable at compile-time.
-Winline
Warn if a function can not be inlined and it was declared as inline. Even with this option, the
compiler will not warn about failures to inline functions declared in system headers.
The compiler uses a variety of heuristics to determine whether or not to inline a function. For
example, the compiler takes into account the size of the function being inlined and the the amount
of inlining that has already been done in the current function. Therefore, seemingly insignificant
changes in the source program can cause the warnings produced by
disappear.
-Wno-invalid-offsetof (C++ only)
Suppress warnings from applying the
1998 ISO C++ standard, applying
implementations, however,
certain kinds of non-POD types. (Such as a simple
by virtue of having a constructor.) This flag is for users who are aware that they are writing
nonportable code and who have deliberately chosen to ignore the warning about it.
The restrictions on
-Winvalid-pch
Warn if a precompiled header (Section 4.20 Using Precompiled Headers) is found in the search
path but can't be used.
-Wlong-long
Warn if
long long
-Wno-long-long
when
-pedantic
declaration is encountered within a function.
because in a debugging version of a program there is often
-Wall
offsetof
offsetof
typically gives meaningful results even when applied to
offsetof
may be relaxed in a future version of the C++ standard.
offsetof
type is used. This is default. To inhibit the warning messages, use
. Flags
-Wlong-long
flag is used.
Chapter 4. GCC Command Options
macro to a non-POD type. According to the
to a non-POD type is undefined. In existing C++
that fails to be a POD type only
struct
and
-Wno-long-long
to appear or
-Winline
are taken into account only