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下面的函数定义的代码是什么意思？？谁能帮小弟我分析下，我很多地方看不懂``````谢谢！！！

int
XRE_main(int argc, char* argv[], const nsXREAppData* aAppData)
{
nsresult rv;
NS_TIMELINE_MARK("enter main");

#ifdef DEBUG
if (PR_GetEnv("XRE_MAIN_BREAK"))
NS_BREAK();
#endif

#ifdef XP_WIN32
// Suppress the "DLL Foo could not be found" dialog, such that if dependent
// libraries (such as GDI+) are not preset, we gracefully fail to load those
// XPCOM components, instead of being ungraceful.
SetErrorMode(SEM_FAILCRITICALERRORS);

#ifdef DEBUG
// Disable small heap allocator to get heapwalk() giving us
// accurate heap numbers. Win2k non-debug does not use small heap allocator.
// Win2k debug seems to be still using it.
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