[PATCH 06/15] Add "maint set dwarf synchronous"

[Tom Tromey <tom@tromey.com>]

For testing, it's sometimes convenient to be able to request that
DWARF reading be done synchronously.  This patch adds a new "maint"
setting for this purpose.
---
 gdb/NEWS            |  3 +++
 gdb/doc/gdb.texinfo | 14 ++++++++++++++
 gdb/dwarf2/read.c   | 23 +++++++++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index 95663433f1c..088651a359b 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -9,6 +9,9 @@
 * GDB index now contains information about the main function.  This speeds up
   startup when it is being used for some large binaries.
 
+* DWARF reading is now done in the background, resulting in faster startup.
+  This can be controlled using "maint set dwarf synchronous".
+
 * Python API
 
   ** New function gdb.notify_mi(NAME, DATA), that emits custom
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index db1a82ec838..78fe5a27ff5 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -41692,6 +41692,20 @@ compilation units will be stored in memory longer, and more total
 memory will be used.  Setting it to zero disables caching, which will
 slow down @value{GDBN} startup, but reduce memory consumption.
 
+@kindex maint set dwarf synchronous
+@kindex maint show dwarf synchronous
+@item maint set dwarf synchronous
+@itemx maint show dwarf synchronous
+Control whether DWARF is read asynchronously.
+
+By default, the DWARF reader is mostly asynchronous with respect to
+the rest of @value{GDBN}.  That is, the bulk of the reading is done in
+the background, and @value{GDBN} will only pause for completion of
+this task when absolutely necessary.
+
+When this setting is enabled, @value{GDBN} will instead wait for DWARF
+processing to complete before continuing.
+
 @kindex maint set dwarf unwinders
 @kindex maint show dwarf unwinders
 @item maint set dwarf unwinders
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index e8cd4496395..8ee6c6d4762 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -739,6 +739,16 @@ show_dwarf_max_cache_age (struct ui_file *file, int from_tty,
 		      "DWARF compilation units is %s.\n"),
 	      value);
 }
+
+/* Wait for DWARF reading to be complete.  */
+static bool dwarf_synchronous = false;
+static void
+show_dwarf_synchronous (struct ui_file *file, int from_tty,
+			struct cmd_list_element *c, const char *value)
+{
+  gdb_printf (file, _("Whether DWARF reading is synchronous is %s.\n"),
+	      value);
+}
 \f
 /* local function prototypes */
 
@@ -21899,6 +21909,19 @@ caching, which can slow down startup."),
 			    &set_dwarf_cmdlist,
 			    &show_dwarf_cmdlist);
 
+  add_setshow_boolean_cmd ("synchronous", class_obscure,
+			    &dwarf_synchronous, _("\
+Set whether DWARF is read synchronously."), _("\
+Show DWARF is read synchronously."), _("\
+By default, DWARF information is read in worker threads,\n\
+and gdb will not generally wait for this process to complete.\n\
+Enabling this setting will cause the DWARF reader to always wait\n\
+for completion before gdb can proceed."),
+			    nullptr,
+			    show_dwarf_synchronous,
+			    &set_dwarf_cmdlist,
+			    &show_dwarf_cmdlist);
+
   add_setshow_zuinteger_cmd ("dwarf-read", no_class, &dwarf_read_debug, _("\
 Set debugging of the DWARF reader."), _("\
 Show debugging of the DWARF reader."), _("\
-- 
2.41.0