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Rewrite wxLogXXX() macros to avoid "ambiguous else" warnings.

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Use a dummy for loop instead of an if statement to avoid all problems with the
dangling else clauses: both the need for an artificially inversed "if" to make
the code like

	if ( something )
		wxLogError("...");
	else
		something-else;

to work as expected and to avoid warnings given by some versions of g++ and
clang for the code above advising to add explicit braces.

Closes #11829.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74735 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin 2013-08-31 17:41:16 +00:00
parent 7980868347
commit 66b370d05f
2 changed files with 36 additions and 15 deletions
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29
include/wx/log.h
View File

@ -12,6 +12,7 @@
#define _WX_LOG_H_
#include "wx/defs.h"
#include "wx/cpp.h"
// ----------------------------------------------------------------------------
// types
@ -1329,29 +1330,27 @@ WXDLLIMPEXP_BASE const wxChar* wxSysErrorMsg(unsigned long nErrCode = 0);
// following arguments are not even evaluated which is good as it avoids
// unnecessary overhead)
//
// Note: the strange if/else construct is needed to make the following code
// Note: the strange (because executing at most once) for() loop because we
// must arrange for wxDO_LOG() to be at the end of the macro and using a
// more natural "if (IsLevelEnabled()) wxDO_LOG()" would result in wrong
// behaviour for the following code ("else" would bind to the wrong "if"):
//
// if ( cond )
// wxLogError("!!!");
// else
// ...
//
// work as expected, without it the second "else" would match the "if"
// inside wxLogError(). Unfortunately code like
//
// if ( cond )
// wxLogError("!!!");
//
// now provokes "suggest explicit braces to avoid ambiguous 'else'"
// warnings from g++ 4.3 and later with -Wparentheses on but they can be
// easily fixed by adding curly braces around wxLogError() and at least
// the code still does do the right thing.
#define wxDO_LOG_IF_ENABLED(level) \
if ( !wxLog::IsLevelEnabled(wxLOG_##level, wxLOG_COMPONENT) ) \
{} \
else \
// See also #11829 for the problems with other simpler approaches,
// notably the need for two macros due to buggy __LINE__ in MSVC.
#define wxDO_LOG_IF_ENABLED_HELPER(level, loopvar) \
for ( bool loopvar = false; \
!loopvar && wxLog::IsLevelEnabled(wxLOG_##level, wxLOG_COMPONENT); \
loopvar = true ) \
wxDO_LOG(level)
#define wxDO_LOG_IF_ENABLED(level) \
wxDO_LOG_IF_ENABLED_HELPER(level, wxMAKE_UNIQUE_NAME(wxlogcheck))
// wxLogFatalError() is special as it can't be disabled
#define wxLogFatalError wxDO_LOG(FatalError)
#define wxVLogFatalError(format, argptr) wxDO_LOGV(FatalError, format, argptr)

22
tests/log/logtest.cpp
View File

@ -169,6 +169,7 @@ private:
CPPUNIT_TEST( CompatLogger2 );
#endif // WXWIN_COMPATIBILITY_2_8
CPPUNIT_TEST( SysError );
CPPUNIT_TEST( NoWarnings );
CPPUNIT_TEST_SUITE_END();
void Functions();
@ -182,6 +183,7 @@ private:
void CompatLogger2();
#endif // WXWIN_COMPATIBILITY_2_8
void SysError();
void NoWarnings();
TestLog *m_log;
wxLog *m_logOld;
@ -362,3 +364,23 @@ void LogTestCase::SysError()
#endif // __MINGW32__
}
void LogTestCase::NoWarnings()
{
// Check that "else" branch is [not] taken as expected and that this code
// compiles without warnings (which used to not be the case).
bool b = wxFalse;
if ( b )
wxLogError("Not logged");
else
b = !b;
CPPUNIT_ASSERT( b );
if ( b )
wxLogError("If");
else
CPPUNIT_FAIL("Should not be taken");
CPPUNIT_ASSERT_EQUAL( "If", m_log->GetLog(wxLOG_Error) );
}