Try to make scope info logging more robust.

Add checks for validity of Vehicle ptrs in scope_dumper::VehicleInfo.
In Unix mode, try to handle SIGSEGVs when dumping scope info.

src/crashlog.cpp

@@ -81,6 +81,13 @@ char *CrashLog::LogCompiler(char *buffer, const char *last) const
 	return buffer;
 }
 
+#ifdef USE_SCOPE_INFO
+/* virtual */ char *CrashLog::LogScopeInfo(char *buffer, const char *last) const
+{
+	return buffer + WriteScopeLog(buffer, last);
+}
+#endif
+
 /**
  * Writes OpenTTD's version to the buffer.
  * @param buffer The begin where to write at.

src/crashlog.h

@@ -80,6 +80,16 @@ protected:
 	 */
 	virtual char *LogModules(char *buffer, const char *last) const;
 
+#ifdef USE_SCOPE_INFO
+	/**
+	 * Writes the scope info log to the buffer.
+	 * This may only be called when IsMainThread() returns true
+	 * @param buffer The begin where to write at.
+	 * @param last   The last position in the buffer to write to.
+	 * @return the position of the \c '\0' character after the buffer.
+	 */
+	virtual char *LogScopeInfo(char *buffer, const char *last) const;
+#endif
 
 	char *LogOpenTTDVersion(char *buffer, const char *last) const;
 	char *LogConfiguration(char *buffer, const char *last) const;

src/os/unix/crashlog_unix.cpp

@@ -251,6 +251,38 @@ class CrashLogUnix : public CrashLog {
 #endif
 		return buffer + seprintf(buffer, last, "\n");
 	}
+
+#if defined(USE_SCOPE_INFO) && defined(__GLIBC__)
+	/**
+	 * This is a wrapper around the generic LogScopeInfo function which sets
+	 * up a signal handler to catch any SIGSEGVs which may occur due to invalid data
+	 */
+	/* virtual */ char *LogScopeInfo(char *buffer, const char *last) const
+	{
+		logStacktraceSavedBuffer = buffer;
+
+		if (setjmp(logStacktraceJmpBuf) != 0) {
+			buffer = logStacktraceSavedBuffer;
+			buffer += seprintf(buffer, last, "\nSomething went seriously wrong when attempting to dump the scope info (SIGSEGV in signal handler).\n");
+			buffer += seprintf(buffer, last, "This is probably due to an invalid pointer or other corrupt data.\n\n");
+			return buffer;
+		}
+
+		signal(SIGSEGV, LogStacktraceSigSegvHandler);
+		sigset_t sigs;
+		sigset_t oldsigs;
+		sigemptyset(&sigs);
+		sigaddset(&sigs, SIGSEGV);
+		sigprocmask(SIG_UNBLOCK, &sigs, &oldsigs);
+
+		buffer = this->CrashLog::LogScopeInfo(buffer, last);
+
+		signal(SIGSEGV, SIG_DFL);
+		sigprocmask(SIG_SETMASK, &oldsigs, NULL);
+		return buffer;
+	}
+#endif
+
 public:
 	/**
 	 * A crash log is always generated by signal.

src/scope_info.cpp

@@ -56,10 +56,18 @@ const char *scope_dumper::VehicleInfo(const Vehicle *v)
 	const char *last = lastof(this->buffer);
 	if (v) {
 		b += seprintf(b, last, "veh: %u: (", v->index);
+		if (Vehicle::GetIfValid(v->index) != v) {
+			b += seprintf(b, last, "INVALID PTR: %p)", v);
+			return this->buffer;
+		}
 		SetDParam(0, v->index);
 		b = GetString(b, STR_VEHICLE_NAME, last);
 		if (v->First() && v->First() != v) {
 			b += seprintf(b, last, "), front: %u: (", v->First()->index);
+			if (Vehicle::GetIfValid(v->First()->index) != v->First()) {
+				b += seprintf(b, last, "INVALID PTR: %p)", v->First());
+				return this->buffer;
+			}
 			SetDParam(0, v->First()->index);
 			b = GetString(b, STR_VEHICLE_NAME, last);
 		}