ON_BLOCK_EXIT and e.g. C4189
in [C++]
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From: Goran on 4 Dec 2008 02:01 Hi all! When using ON_BLOCK_EXIT(_OBJ) of ScopeGuard, compiler is emitting a warning for unused variable. E.g. MS C++ compiler says: warning C4189: 'scopeGuard44' : local variable is initialized but not referenced Clearly, that can be suppressed using #pragma warning for that compiler. I'd like to avoid that, because: 1. I like to know about other unused variables :-), 2. better be compiler-independent, if possible. 3. if I do use #pragma warning(disable:4189) and #pragma warning (default:4189), the "default" pragma must be outside the function scope for it to work (not even outside scope, but outside __function__ scope, tsk, tsk, MS). So... Any idea of how to do that? TIA, Goran. -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Gert-Jan de Vos on 5 Dec 2008 21:32 On Dec 4, 8:01 pm, Goran <goran.pu...(a)gmail.com> wrote: > Hi all! > > When using ON_BLOCK_EXIT(_OBJ) of ScopeGuard, compiler is emitting a > warning for unused variable. Depending on your specific ON_BLOCK_EXIT definition, you could change the definition of ON_BLOCK_EXIT to something like: #define ON_SCOPE_EXIT(f) scope_guard ANONYMOUS_VARIABLE(guard__) = make_guard(f); static_cast<void>(ANONYMOUS_VARIABLE(guard__)) This works for me on VS2005 For gcc this may work: #define ON_SCOPE_EXIT(f) scope_guard ANONYMOUS_VARIABLE(guard__) __attribute__ ((unused)) = make_guard(f) -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Goran on 9 Dec 2008 09:47 On Dec 6, 3:32 pm, Gert-Jan de Vos <gert- jan.de....(a)onsneteindhoven.nl> wrote: > On Dec 4, 8:01 pm, Goran <goran.pu...(a)gmail.com> wrote: > > > Hi all! > > > When using ON_BLOCK_EXIT(_OBJ) of ScopeGuard, compiler is emitting a > > warning for unused variable. > > Depending on your specific ON_BLOCK_EXIT definition, you could change > the definition of ON_BLOCK_EXIT to something like: > > #define ON_SCOPE_EXIT(f) scope_guard ANONYMOUS_VARIABLE(guard__) = > make_guard(f); static_cast<void>(ANONYMOUS_VARIABLE(guard__)) > > This works for me on VS2005 > > For gcc this may work: > > #define ON_SCOPE_EXIT(f) scope_guard ANONYMOUS_VARIABLE(guard__) > __attribute__ ((unused)) = make_guard(f) I just got around to trying this. Unfortunately, your idea works only if you guard something with a function with no arguments. My ScopeGuard is like this (I think that's exactly what's in CUJ article where it appeared: #define ON_BLOCK_EXIT ScopeGuard ANONYMOUS_VARIABLE(scopeGuard) = MakeGuard I am already using ON_BLOCK_EXIT with multiple parameters and with ByRef, e.g. like so: ON_BLOCK_EXIT(&MyResourceDisposal, param1, ByRef(param2)) But thanks for an effort! -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Boris Rasin on 14 Dec 2008 09:34
On Dec 4, 9:01 pm, Goran <goran.pu...(a)gmail.com> wrote: > Hi all! > > When using ON_BLOCK_EXIT(_OBJ) of ScopeGuard, compiler is emitting a > warning for unused variable. > > E.g. MS C++ compiler says: > > warning C4189: 'scopeGuard44' : local variable is initialized but not > referenced > > Clearly, that can be suppressed using #pragma warning for that > compiler. I'd like to avoid that, because: > > 1. I like to know about other unused variables :-), > > 2. better be compiler-independent, if possible. > > 3. if I do use #pragma warning(disable:4189) and #pragma warning > (default:4189), the "default" pragma must be outside the function > scope for it to work (not even outside scope, but outside __function__ > scope,tsk,tsk, MS). > > So... > > Any idea of how to do that? Perhaps __pragma(warning) keyword would work instead of #pragma warning. -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] |