Provide dbgs(), a circular-buffering debug output stream. By default it
simply passes output to errs(). If -debug-buffer-size=N is set N > 0,
dbgs() buffers its output until program termination and dumps the last N
characters sent to it. This is handy when debugging very large inputs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92002 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Debug.cpp b/lib/Support/Debug.cpp
index 50abe01..12b38c7 100644
--- a/lib/Support/Debug.cpp
+++ b/lib/Support/Debug.cpp
@@ -25,6 +25,9 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/circular_raw_ostream.h"
+#include "llvm/System/Signals.h"
+
using namespace llvm;
// All Debug.h functionality is a no-op in NDEBUG mode.
@@ -37,6 +40,16 @@
Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
cl::location(DebugFlag));
+// -debug-buffer-size - Buffer the last N characters of debug output
+//until program termination.
+static cl::opt<unsigned>
+DebugBufferSize("debug-buffer-size",
+ cl::desc("Buffer the last N characters of debug output"
+ "until program termination. "
+ "[default 0 -- immediate print-out]"),
+ cl::Hidden,
+ cl::init(0));
+
static std::string CurrentDebugType;
static struct DebugOnlyOpt {
void operator=(const std::string &Val) const {
@@ -50,6 +63,18 @@
cl::Hidden, cl::value_desc("debug string"),
cl::location(DebugOnlyOptLoc), cl::ValueRequired);
+// Signal handlers - dump debug output on termination.
+static void debug_user_sig_handler(void *Cookie)
+{
+ // This is a bit sneaky. Since this is under #ifndef NDEBUG, we
+ // know that debug mode is enabled and dbgs() really is a
+ // circular_raw_ostream. If NDEBUG is defined, then dbgs() ==
+ // errs() but this will never be invoked.
+ llvm::circular_raw_ostream *dbgout =
+ static_cast<llvm::circular_raw_ostream *>(&llvm::dbgs());
+ dbgout->flushBufferWithBanner();
+}
+
// isCurrentDebugType - Return true if the specified string is the debug type
// specified on the command line, or if none was specified on the command line
// with the -debug-only=X option.
@@ -66,9 +91,38 @@
CurrentDebugType = Type;
}
+/// dbgs - Return a circular-buffered debug stream.
+raw_ostream &llvm::dbgs() {
+ // Do one-time initialization in a thread-safe way.
+ static struct dbgstream {
+ circular_raw_ostream strm;
+
+ dbgstream() :
+ strm(errs(), "*** Debug Log Output ***\n",
+ (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
+ if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
+ // TODO: Add a handler for SIGUSER1-type signals so the user can
+ // force a debug dump.
+ sys::AddSignalHandler(&debug_user_sig_handler, 0);
+ // Otherwise we've already set the debug stream buffer size to
+ // zero, disabling buffering.
+ }
+ } thestrm;
+
+ return thestrm.strm;
+}
+
#else
// Avoid "has no symbols" warning.
namespace llvm {
-int Debug_dummy = 0;
+ /// dbgs - Return dbgs().
+ raw_ostream &dbgs() {
+ return dbgs();
+ }
}
+
#endif
+
+/// EnableDebugBuffering - Turn on signal handler installation.
+///
+bool llvm::EnableDebugBuffering = false;