On Monday 21 December 2009 10:14, Török Edwin wrote:> On 2009-12-21 18:06, David Greene wrote:
> > On Saturday 19 December 2009 00:16, Chris Lattner wrote:
> >>> Or I think I can just assume (Yikes!) that if the signal
handler is
> >>> invoked it will really be a circular_raw_ostream since the
handler
> >>> should (!) only be set up in debug mode.
> >>>
> >>> That scares me a bit, though.
> >>
> >> Why don't you just check #ifndef NDEBUG like the code that
sets it up?
> >
> > Next iteration.
>
> Will this setup a signal handler in a Release+Asserts build?
> That is not very nice, a library shouldn't setup signal handlers,
except
> in debug mode.
Here's a revision. It only adds the handler if DisableDebugBuffering is
false, DebugFlag is true and the debug buffer size is non-zero.
-Dave
Index: include/llvm/Support/Debug.h
==================================================================---
include/llvm/Support/Debug.h (revision 91825)
+++ include/llvm/Support/Debug.h (working copy)
@@ -28,6 +28,8 @@
namespace llvm {
+class raw_ostream;
+
/// DEBUG_TYPE macro - Files can specify a DEBUG_TYPE as a string, which
causes
/// all of their DEBUG statements to be activatable with
-debug-only=thatstring.
#ifndef DEBUG_TYPE
@@ -58,7 +60,7 @@
/// this is a debug build, then the code specified as the option to the macro
/// will be executed. Otherwise it will not be. Example:
///
-/// DEBUG_WITH_TYPE("bitset", errs() << "Bitset contains:
" << Bitset <<
"\n");
+/// DEBUG_WITH_TYPE("bitset", dbgs() << "Bitset contains:
" << Bitset <<
"\n");
///
/// This will emit the debug information if -debug is present, and
-debug-only
/// is not specified, or is specified as "bitset".
@@ -72,15 +74,28 @@
#define DEBUG_WITH_TYPE(TYPE, X) do { } while (0)
#endif
+/// DisableDebugBuffering - This defaults to false. If true, the
+/// debug stream will not install signal handlers and thus will not
+/// buffer any output since there will be no way to get at it. It
+/// allows clients to disable signal handler install in case of a
+/// conflict
+///
+extern bool DisableDebugBuffering;
+
+/// dbgs() - This returns a reference to a raw_ostream for debugging
+/// messages. If debugging is disabled it returns dbgs(). Use it
+/// like: dbgs() << "foo" << "bar";
+raw_ostream &dbgs();
+
// DEBUG macro - This macro should be used by passes to emit debug
information.
// In the '-debug' option is specified on the commandline, and if this
is a
// debug build, then the code specified as the option to the macro will be
// executed. Otherwise it will not be. Example:
//
-// DEBUG(errs() << "Bitset contains: " << Bitset <<
"\n");
+// DEBUG(dbgs() << "Bitset contains: " << Bitset <<
"\n");
//
#define DEBUG(X) DEBUG_WITH_TYPE(DEBUG_TYPE, X)
-
+
} // End llvm namespace
#endif
Index: lib/Support/Debug.cpp
==================================================================---
lib/Support/Debug.cpp (revision 91825)
+++ lib/Support/Debug.cpp (working copy)
@@ -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;
}
+/// DisableDebugBuffering - Turn off signal handler installation.
+///
+bool llvm::DisableDebugBuffering = false;
+
+/// 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(),
+ (DisableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
+ if (!DisableDebugBuffering && 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