[LOGCXX-393] Strange compile error w/ log4cxx, version 0.10.0,gcc version 4.2.1 20070719 [FreeBSD]

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.10.0
• Environment: gcc 4.2.1; FreeBSD 8.2-RELEASE-p4 (amd64)
• Assignee: Curt Arnold
• Reporter: Jim Carroll
• Created: 06/Feb/12 19:03
• Updated: 10/Feb/14 14:59
• Resolved: 10/Feb/14 14:59

Description

Quite strange (but minor) issue using log4cxx. The following code snippet fails to compile:

#include <log4cxx/logger.h>
log4cxx::LoggerPtr logger = log4cxx::Logger::getLogger("fn");
void fn()

{ if (logger->isTraceEnabled()) LOG4CXX_TRACE(logger, "Trace"); else if (logger->isDebugEnabled()) LOG4CXX_DEBUG(logger, "Debug"); }

Compiled with the following command: g++ -c -I/usr/local/include t2.cpp

Results in:

t2.cpp: In function 'void fn()':
t2.cpp:6: error: expected primary-expression before 'else'
t2.cpp:6: error: expected `;' before 'else'
t2.cpp:8: error: expected `}' at end of input

You can solve the compile error, by enclosing the LOG4CXX_TRACE statement in braces, thusly:

#include <log4cxx/logger.h>
log4cxx::LoggerPtr logger = log4cxx::Logger::getLogger("fn");
void fn() {
if (logger->isTraceEnabled())

{ LOG4CXX_TRACE(logger, "Trace"); }

else if (logger->isDebugEnabled())
LOG4CXX_DEBUG(logger, "Debug");
}

Here's where it get's really strange....the compiler only generates the error, when you have the 'else if' statement immediately following the LOG4CXX_TRACE() macro. So this piece of code also compiles without errors.

#include <log4cxx/logger.h>
log4cxx::LoggerPtr logger = log4cxx::Logger::getLogger("fn");
void fn()

{ if (logger->isTraceEnabled()) LOG4CXX_TRACE(logger, "Trace"); }

I strongly suspect it's some sort of strange artifact of the pre-processor, but I'm having difficulty figuring out what it specifically doesn't like. I've attached the pre-processor output below.

Jim C.

---

(REMOVED MOST OF THE CPP OUTPUT FOR BREVITY)

1. 1910 "/usr/local/include/log4cxx/logger.h" 2
2. 2 "t2.cpp" 2
   log4cxx::LoggerPtr logger = log4cxx::Logger::getLogger("fn");
   void fn() {
   if (logger->isTraceEnabled())
   { if (_builtin_expect(logger->isTraceEnabled(), 0)) { ::log4cxx::helpers::MessageBuffer oss; logger->forcedLog(::log4cxx::Level::getTrace(), oss_.str(oss_ << "Trace"), ::log4cxx::spi::LocationInfo("t2.cpp", _PRETTY_FUNCTION_, 5)); }};
   else if (logger->isDebugEnabled())
   { if (_builtin_expect(logger->isDebugEnabled(), 0)) { ::log4cxx::helpers::MessageBuffer oss; logger->forcedLog(::log4cxx::Level::getDebug(), oss_.str(oss_ << "Debug"), ::log4cxx::spi::LocationInfo("t2.cpp", _PRETTY_FUNCTION_, 7)); }};
   }

Issue Links

• duplicates: LOGCXX-319 Please make sure that the LOG4CXX_* macro's can be used as ordinary statements.