Why adding a DPRINTF(XXX debug flag fails with "error:'XXX' was not declared in this scope" in gem5?

I want to know the cache information when the replacement algorithm is executed. So I made the following changes in the latest version of gem5. I added a line of DebugFlag('ReplacementInfo') command to the /home/cuiyujie/workspace/workGem5/gem5/src/mem/cache/replacement_policies/SConscript file. Then I added the header file #include "debug/ReplacementInfo.hh" in the /home/cuiyujie/workspace/workGem5/gem5/build/X86/params/RandomRP.cc file. Then I used DPRINTF(ReplacementInfo, "candidates"); command in this file. But an error occurred during compilation.

build/X86/mem/cache/replacement_policies/random_rp.cc: In member function'virtual ReplaceableEntry* RandomRP::getVictim(const ReplacementCandidates&) const':
build/X86/mem/cache/replacement_policies/random_rp.cc:82:13: error:'ReplacementInfo' was not declared in this scope
     DPRINTF(ReplacementInfo, "candidates");
             ^
build/X86/mem/cache/replacement_policies/random_rp.cc:82:13: note: suggested alternative:
In file included from build/X86/mem/cache/replacement_policies/random_rp.cc:44:0:
build/X86/debug/ReplacementInfo.hh:18:19: note:'Debug::ReplacementInfo'
 extern SimpleFlag ReplacementInfo;
                   ^
build/X86/mem/cache/replacement_policies/random_rp.cc:82:42: error:'DPRINTF' was not declared in this scope
     DPRINTF(ReplacementInfo, "candidates");
                                          ^
scons: *** [build/X86/mem/cache/replacement_policies/random_rp.o] Error 1
scons: building terminated because of errors.

Solution

The second error was:

build/X86/mem/cache/replacement_policies/random_rp.cc:82:42: error:'DPRINTF' was not declared in this scope
     DPRINTF(ReplacementInfo, "candidates");

which means you also need:

#include "base/trace.hh"

which is where DPRINTF is defined.

Error order is a bit messed up because GCC must be assuming that DPRINTF is a function since it did not see the macro definition, so it tries to evaluate arguments first. But DPRINTF is a macro, and adds the missing Debug:: to Debug::ReplacementInfo, which it complained about on the first error:

#define DPRINTF(x, ...) do {                     \
    using namespace Debug;                       \
    if (M5_UNLIKELY(DTRACE(x))) {                \
        Trace::getDebugLogger()->dprintf_flag(   \
            curTick(), name(), #x, __VA_ARGS__); \
    }                                            \
} while (0)