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Go patch committed: Turn on debug info by default

Message ID CAOyqgcV823xQK1jNqmeS+C+pC3Rx9mb_BqsCTn6ONMp-TKdG0w@mail.gmail.com
State New
Headers show

Commit Message

Ian Lance Taylor Jan. 23, 2015, 10:26 p.m. UTC 
Go programs assume that they can always find the location that called
them, via standard library functions like
http://golang.org/pkg/runtime/#Caller .  In gccgo this is implemented
via libbacktrace, which uses debug info.  This means that many Go
programs only works correctly if compiled with -g.  As suggested in PR
64595, this patch changes the gccgo driver to turn on -g1 by default.
You can still use -g0 to disable debug info generation, or of course
you can strip the binary.  Bootstrapped and ran Go testsuite on
x86_64-unknown-linux-gnu.  Committed to mainline.

Ian


2015-01-23  Ian Lance Taylor  <iant@google.com>

PR go/64595
* go-lang.c (go_langhook_init_options_struct): Set default
debug_info_level.
(go_langhook_post_options): If debug_info_level is still the
default, make sure write_symbols is set.
* gccgo.texi (Invoking gccgo): Document that -g1 is the default.
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Patch

Index: gcc/go/gccgo.texi
===================================================================
--- gcc/go/gccgo.texi	(revision 219876)
+++ gcc/go/gccgo.texi	(working copy)
@@ -223,6 +223,18 @@  may be used.  Or the checks may be remov
 @option{-fno-go-check-divide-overflow}.  This option is currently on
 by default, but in the future may be off by default on systems that do
 not require it.
+
+@item -g
+@cindex @option{-g for gccgo}
+This is the standard @command{gcc} option (@pxref{Debugging Options, ,
+Debugging Options, gcc, Using the GNU Compiler Collection (GCC)}).  It
+is mentioned here because by default @command{gccgo} turns on
+debugging information generation with the equivalent of the standard
+option @option{-g1}.  This is because Go programs require debugging
+information to be available in order to get backtrace information.  An
+explicit @option{-g0} may be used to disable the generation of
+debugging information, in which case certain standard library
+functions, such as @code{runtime.Callers}, will not operate correctly.
 @end table
 
 @c man end
Index: gcc/go/go-lang.c
===================================================================
--- gcc/go/go-lang.c	(revision 219876)
+++ gcc/go/go-lang.c	(working copy)
@@ -171,6 +171,12 @@  go_langhook_init_options_struct (struct
   /* Exceptions are used to handle recovering from panics.  */
   opts->x_flag_exceptions = 1;
   opts->x_flag_non_call_exceptions = 1;
+
+  /* Go programs expect runtime.Callers to work, and that uses
+     libbacktrace that uses debug info.  Set the debug info level to 1
+     by default.  In post_options we will set the debug type if the
+     debug info level was not set back to 0 on the command line.  */
+  opts->x_debug_info_level = DINFO_LEVEL_TERSE;
 }
 
 /* Infrastructure for a vector of char * pointers.  */
@@ -289,6 +295,12 @@  go_langhook_post_options (const char **p
   if (!global_options_set.x_flag_optimize_sibling_calls)
     global_options.x_flag_optimize_sibling_calls = 0;
 
+  /* If the debug info level is still 1, as set in init_options, make
+     sure that some debugging type is selected.  */
+  if (global_options.x_debug_info_level == DINFO_LEVEL_TERSE
+      && global_options.x_write_symbols == NO_DEBUG)
+    global_options.x_write_symbols = PREFERRED_DEBUGGING_TYPE;
+
   /* Returning false means that the backend should be used.  */
   return false;
 }