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 <i...@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.
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; }