From f3ea057c1bedbba987b8187a4e4839bc3e98c13a Mon Sep 17 00:00:00 2001
From: "beard%netscape.com" <beard%netscape.com>
Date: Fri, 1 Sep 2000 03:15:30 +0000
Subject: [PATCH] added RTTI heuristics for Linux.

---
 gc/boehm/typeinfo.cpp | 129 +++++++++++++++++++++++++++++++-----------
 1 file changed, 97 insertions(+), 32 deletions(-)

diff --git a/gc/boehm/typeinfo.cpp b/gc/boehm/typeinfo.cpp
index f429d6f9cf9..cdaac6246da 100644
--- a/gc/boehm/typeinfo.cpp
+++ b/gc/boehm/typeinfo.cpp
@@ -1,59 +1,124 @@
 /*
-	typeinfo.cpp
+  typeinfo.cpp
 	
-	Speculatively use RTTI on a random object. If it contains a pointer at offset 0
-	that is in the current process' address space, and that so on, then attempt to
-	use C++ RTTI's typeid operation to obtain the name of the type.
-	
-	by Patrick C. Beard.
+  Speculatively use RTTI on a random object. If it contains a pointer at offset 0
+  that is in the current process' address space, and that so on, then attempt to
+  use C++ RTTI's typeid operation to obtain the name of the type.
+  
+  by Patrick C. Beard.
  */
 
 #include <typeinfo>
 #include <ctype.h>
-#include <Processes.h>
+
+#include "gcconfig.h"
 
 extern "C" const char* getTypeName(void* ptr);
 
+class IUnknown {
+public:
+    virtual long QueryInterface() = 0;
+    virtual long AddRef() = 0;
+    virtual long Release() = 0;
+};
+
+#if defined(MACOS)
+
+#include <Processes.h>
+
 class AddressSpace {
 public:
-	AddressSpace();
-	Boolean contains(void* ptr);
+    AddressSpace();
+    Boolean contains(void* ptr);
 private:
-	ProcessInfoRec mInfo;
+    ProcessInfoRec mInfo;
 };
 
 AddressSpace::AddressSpace()
 {
-	ProcessSerialNumber psn = { 0, kCurrentProcess };
-	mInfo.processInfoLength = sizeof(mInfo);
-	::GetProcessInformation(&psn, &mInfo);
+    ProcessSerialNumber psn = { 0, kCurrentProcess };
+    mInfo.processInfoLength = sizeof(mInfo);
+    ::GetProcessInformation(&psn, &mInfo);
 }
 
 Boolean AddressSpace::contains(void* ptr)
 {
-	UInt32 start = UInt32(mInfo.processLocation);
-	return (UInt32(ptr) >= start && UInt32(ptr) < (start + mInfo.processSize));
+    UInt32 start = UInt32(mInfo.processLocation);
+    return (UInt32(ptr) >= start && UInt32(ptr) < (start + mInfo.processSize));
 }
 
-class IUnknown {
-	virtual long QueryInterface() = 0;
-	virtual long AddRef() = 0;
-	virtual long Release() = 0;
-};
-
 const char* getTypeName(void* ptr)
 {
-	// construct only one of these per process.
-	static AddressSpace space;
+    // construct only one of these per process.
+    static AddressSpace space;
 	
-	// sanity check the vtable pointer, before trying to use RTTI on the object.
-	void** vt = *(void***)ptr;
-	if (space.contains(vt) && space.contains(*vt)) {
-		IUnknown* u = static_cast<IUnknown*>(ptr);
-		const char* type = typeid(*u).name();
+    // sanity check the vtable pointer, before trying to use RTTI on the object.
+    void** vt = *(void***)ptr;
+    if (vt && !(unsigned(vt) & 0x3) && space.contains(vt) && space.contains(*vt)) {
+	IUnknown* u = static_cast<IUnknown*>(ptr);
+	const char* type = typeid(*u).name();
         // make sure it looks like a C++ identifier.
-		if (type && (isalnum(type[0]) || type[0] == '_'))
-		    return type;
-	}
-	return "void*";
+	if (type && (isalnum(type[0]) || type[0] == '_'))
+	    return type;
+    }
+    return "void*";
 }
+
+#endif
+
+#if defined(LINUX)
+
+#include <signal.h>
+#include <setjmp.h>
+
+static jmp_buf context;
+
+static void handler(int signum)
+{
+    longjmp(context, signum);
+}
+
+#define attempt() setjmp(context)
+
+class Signaller {
+public:
+    Signaller(int signum);
+    ~Signaller();
+
+private:
+    typedef void (*handler_t) (int signum);
+    int mSignal;
+    handler_t mOldHandler;
+};
+
+Signaller::Signaller(int signum)
+    : mSignal(signum), mOldHandler(signal(signum, &handler))
+{
+}
+
+Signaller::~Signaller()
+{
+    signal(mSignal, mOldHandler);
+}
+
+const char* getTypeName(void* ptr)
+{
+    // sanity check the vtable pointer, before trying to use RTTI on the object.
+    void** vt = *(void***)ptr;
+    if (vt && !(unsigned(vt) & 3)) {
+	Signaller signaller(SIGSEGV);
+	if (attempt() == 0) {
+	    IUnknown* u = static_cast<IUnknown*>(ptr);
+	    const char* type = typeid(*u).name();
+	    // make sure it looks like a C++ identifier.
+	    if (type && (isalnum(type[0]) || type[0] == '_')) {
+		// ECGS seems to prefix a length string.
+		while (isdigit(*type)) ++type;
+		return type;
+	    }
+	} 
+    }
+    return "void*";
+}
+
+#endif