+ * problem.
+ *
+ * Possible values are:
+ * 0 -- Never show signal-related output. There is absolutely no
+ * run-time overhead from FSHOW_SIGNAL in this case.
+ *
+ * 1 -- (recommended)
+ * Show signal-related output only if selected at run-time
+ * (otherwise almost no run-time overhead).
+ *
+ * 2 -- Unconditionally show signal-related output.
+ * Very significant overhead.
+ *
+ * For reasons of tradition, we default to 0 on POSIX and 1 on Windows
+ * through :SB-QSHOW.
+ *
+ * With option 1, set up environment variable SBCL_DYNDEBUG to include
+ * "fshow" or "fshow_signal" before starting SBCL to enable output.
+ *
+ * There is no particular advantage to option 2 except that you do not
+ * need to set environment variables in this case.
+ */
+#ifdef LISP_FEATURE_SB_QSHOW
+# define QSHOW_SIGNALS 1
+#else
+# define QSHOW_SIGNALS 0
+#endif
+
+/* Enable low-level debugging output, if not zero. Defaults to enabled
+ * if QSHOW_SIGNALS, disabled otherwise. Change it to 1 or 2 if you want
+ * low-level debugging output but not the whole signal mess. */
+#define QSHOW QSHOW_SIGNALS
+
+/*
+ * Configuration options end here -- the following defines do not
+ * generally need customization.
+ */
+
+#define odxprint(topic, fmt, ...) \
+ do \
+ if (dyndebug_config.dyndebug_##topic) \
+ odxprint_fun(fmt "\n", ##__VA_ARGS__); \
+ while (0)
+
+void odxprint_fun(const char *fmt, ...);
+void fshow_fun(void *ignored, const char *fmt, ...);
+
+/* Flags defined in a structure to avoid code duplication between
+ * declaration and definition. */
+extern struct dyndebug_config {
+ int dyndebug_fshow;
+ int dyndebug_fshow_signal;
+ int dyndebug_gencgc_verbose;
+ int dyndebug_safepoints;
+ int dyndebug_seh;
+ int dyndebug_misc;
+ int dyndebug_pagefaults;
+ int dyndebug_backtrace_when_lost;
+ int dyndebug_sleep_when_lost;
+ int dyndebug_io;
+ int dyndebug_runtime_link;
+} dyndebug_config;
+
+#ifdef LISP_FEATURE_GENCGC
+extern int gencgc_verbose;
+#endif
+
+void dyndebug_init(void);
+
+#if QSHOW_SIGNAL_SAFE == 1 && !defined(LISP_FEATURE_WIN32)
+
+extern sigset_t blockable_sigset;
+
+#define QSHOW_BLOCK \
+ sigset_t oldset; \
+ thread_sigmask(SIG_BLOCK, &blockable_sigset, &oldset)
+#define QSHOW_UNBLOCK thread_sigmask(SIG_SETMASK,&oldset,0)
+#else
+#define QSHOW_BLOCK
+#define QSHOW_UNBLOCK
+#endif
+
+/* The following macros duplicate the expansion of odxprint, because the
+ * extra level of parentheses around `args' prevents us from
+ * implementing FSHOW in terms of odxprint directly. (They also differ
+ * in a newline.)
+ */
+
+#if QSHOW
+# define FSHOW(args) \
+ do if (dyndebug_config.dyndebug_fshow) fshow_fun args; while (0)
+# define SHOW(string) FSHOW((stderr, "/%s\n", string))
+#else
+# define FSHOW(args)
+# define SHOW(string)
+#endif
+
+#if QSHOW_SIGNALS
+# define FSHOW_SIGNAL(args) \
+ do if (dyndebug_config.dyndebug_fshow_signal) fshow_fun args; while (0)
+#else
+# define FSHOW_SIGNAL(args)
+#endif