Re: [PATCH] PR debug/38757 gcc does not emit DW_LANG_C99

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, Nov 12, 2014 at 03:50:19PM +0100, Mark Wielaard wrote:
> On Mon, 2014-10-13 at 10:33 +0200, Mark Wielaard wrote:
> > On Wed, 2014-10-08 at 12:13 +0200, Mark Wielaard wrote:
> > > This patch was written a long time ago by Jakub and has been in Fedora
> > > gcc for some time. All I did was rebase it to current gcc trunk
> > > and add a testcase. Back when it was originally proposed the issue was
> > > that because DWARF was generated late adding new lang hooks for this
> > > was problematic for LTO. Now that there is a move towards generating
> > > DWARF early I am hoping this patch can finally make it to mainline gcc.
> > 
> > Ping.
> 
> Ping again.

I think we want this (also extended for C11/C++11/C++14 afterwards), even
when the early debug bits won't be ready for GCC 5; LTO will just continue
claiming to be old C (or whatever it claims right now), but there is
hope it will be improved for GCC 6.

But, I can't approve my own patch...  Richard, can you live with this?

> > > This lang hook will be more useful when DWARFv5 gets out, which is
> > > supposed to define language identifiers for newer C and C++ versions.
> > > 
> > > Previous discussions:
> > > http://gcc.gnu.org/ml/gcc-patches/2009-03/msg00858.html
> > > http://gcc.gnu.org/ml/gcc-patches/2010-04/msg00991.html
> > > 
> > > gcc/ChangeLog
> > > 
> > > 2009-03-18  Jakub Jelinek  <jakub@redhat.com>
> > > 
> > > 	PR debug/38757
> > > 	* langhooks.h (struct lang_hooks): Add source_language langhook.
> > > 	* langhooks-def.h (LANG_HOOKS_SOURCE_LANGUAGE): Define to NULL.
> > > 	(LANG_HOOKS_INITIALIZER): Add LANG_HOOKS_SOURCE_LANGUAGE.
> > > 	* dwarf2out.c (add_prototyped_attribute): Add DW_AT_prototype
> > > 	also for DW_LANG_{C,C99,ObjC}.
> > > 	(gen_compile_unit_die): Use lang_hooks.source_language () to
> > > 	determine if DW_LANG_C99 or DW_LANG_C89 should be returned.
> > > 
> > > gcc/c/ChangeLog
> > > 
> > > 2009-03-18  Jakub Jelinek  <jakub@redhat.com>
> > > 
> > > 	PR debug/38757
> > > 	* c-lang.c (c_source_language): New function.
> > > 	(LANG_HOOKS_SOURCE_LANGUAGE): Define.
> > > 
> > > gcc/testsuite/ChangeLog
> > > 
> > > 2014-10-08  Mark Wielaard  <mjw@redhat.com>
> > > 
> > > 	PR debug/38757
> > > 	* gcc.dg/debug/dwarf2/lang-c89.c: New test.
> > > 	* gcc.dg/debug/dwarf2/lang-c99.c: Likewise.
> > > ---
> > >  gcc/ChangeLog                                | 11 +++++++++++
> > >  gcc/c/ChangeLog                              |  6 ++++++
> > >  gcc/c/c-lang.c                               |  8 ++++++++
> > >  gcc/dwarf2out.c                              | 19 ++++++++++++++++---
> > >  gcc/langhooks-def.h                          |  4 +++-
> > >  gcc/langhooks.h                              |  4 ++++
> > >  gcc/testsuite/ChangeLog                      |  6 ++++++
> > >  gcc/testsuite/gcc.dg/debug/dwarf2/lang-c89.c |  6 ++++++
> > >  gcc/testsuite/gcc.dg/debug/dwarf2/lang-c99.c |  6 ++++++
> > >  9 files changed, 66 insertions(+), 4 deletions(-)
> > >  create mode 100644 gcc/testsuite/gcc.dg/debug/dwarf2/lang-c89.c
> > >  create mode 100644 gcc/testsuite/gcc.dg/debug/dwarf2/lang-c99.c
> > > 
> > > diff --git a/gcc/c/c-lang.c b/gcc/c/c-lang.c
> > > index 97c0443..dadeb1a 100644
> > > --- a/gcc/c/c-lang.c
> > > +++ b/gcc/c/c-lang.c
> > > @@ -35,6 +35,12 @@ along with GCC; see the file COPYING3.  If not see
> > >  
> > >  enum c_language_kind c_language = clk_c;
> > >  
> > > +static int
> > > +c_source_language (void)
> > > +{
> > > +  return flag_isoc99 ? 1999 : 1989;
> > > +}
> > > +
> > >  /* Lang hooks common to C and ObjC are declared in c-objc-common.h;
> > >     consequently, there should be very few hooks below.  */
> > >  
> > > @@ -44,6 +50,8 @@ enum c_language_kind c_language = clk_c;
> > >  #define LANG_HOOKS_INIT c_objc_common_init
> > >  #undef LANG_HOOKS_INIT_TS
> > >  #define LANG_HOOKS_INIT_TS c_common_init_ts
> > > +#undef LANG_HOOKS_SOURCE_LANGUAGE
> > > +#define LANG_HOOKS_SOURCE_LANGUAGE c_source_language
> > >  
> > >  /* Each front end provides its own lang hook initializer.  */
> > >  struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
> > > diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
> > > index 59c05ed..4932cd0 100644
> > > --- a/gcc/dwarf2out.c
> > > +++ b/gcc/dwarf2out.c
> > > @@ -16708,9 +16708,18 @@ add_bit_size_attribute (dw_die_ref die, tree decl)
> > >  static inline void
> > >  add_prototyped_attribute (dw_die_ref die, tree func_type)
> > >  {
> > > -  if (get_AT_unsigned (comp_unit_die (), DW_AT_language) == DW_LANG_C89
> > > -      && prototype_p (func_type))
> > > -    add_AT_flag (die, DW_AT_prototyped, 1);
> > > +  switch (get_AT_unsigned (comp_unit_die (), DW_AT_language))
> > > +    {
> > > +    case DW_LANG_C:
> > > +    case DW_LANG_C89:
> > > +    case DW_LANG_C99:
> > > +    case DW_LANG_ObjC:
> > > +      if (prototype_p (func_type))
> > > +	add_AT_flag (die, DW_AT_prototyped, 1);
> > > +      break;
> > > +    default:
> > > +      break;
> > > +    }
> > >  }
> > >  
> > >  /* Add an 'abstract_origin' attribute below a given DIE.  The DIE is found
> > > @@ -19544,6 +19553,10 @@ gen_compile_unit_die (const char *filename)
> > >  	language = DW_LANG_ObjC;
> > >        else if (strcmp (language_string, "GNU Objective-C++") == 0)
> > >  	language = DW_LANG_ObjC_plus_plus;
> > > +      else if (strcmp (language_string, "GNU C") == 0
> > > +	       && lang_hooks.source_language
> > > +	       && lang_hooks.source_language () >= 1999)
> > > +	language = DW_LANG_C99;
> > >        else if (dwarf_version >= 5 || !dwarf_strict)
> > >  	{
> > >  	  if (strcmp (language_string, "GNU Go") == 0)
> > > diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
> > > index e5ae3e3..b6c8dd4 100644
> > > --- a/gcc/langhooks-def.h
> > > +++ b/gcc/langhooks-def.h
> > > @@ -120,6 +120,7 @@ extern bool lhd_omp_mappable_type (tree);
> > >  #define LANG_HOOKS_BLOCK_MAY_FALLTHRU	hook_bool_const_tree_true
> > >  #define LANG_HOOKS_EH_USE_CXA_END_CLEANUP	false
> > >  #define LANG_HOOKS_DEEP_UNSHARING	false
> > > +#define LANG_HOOKS_SOURCE_LANGUAGE	NULL
> > >  
> > >  /* Attribute hooks.  */
> > >  #define LANG_HOOKS_ATTRIBUTE_TABLE		NULL
> > > @@ -313,7 +314,8 @@ extern void lhd_end_section (void);
> > >    LANG_HOOKS_EH_PROTECT_CLEANUP_ACTIONS, \
> > >    LANG_HOOKS_BLOCK_MAY_FALLTHRU, \
> > >    LANG_HOOKS_EH_USE_CXA_END_CLEANUP, \
> > > -  LANG_HOOKS_DEEP_UNSHARING \
> > > +  LANG_HOOKS_DEEP_UNSHARING, \
> > > +  LANG_HOOKS_SOURCE_LANGUAGE \
> > >  }
> > >  
> > >  #endif /* GCC_LANG_HOOKS_DEF_H */
> > > diff --git a/gcc/langhooks.h b/gcc/langhooks.h
> > > index 32e76f9..0022516 100644
> > > --- a/gcc/langhooks.h
> > > +++ b/gcc/langhooks.h
> > > @@ -485,6 +485,10 @@ struct lang_hooks
> > >       gimplification.  */
> > >    bool deep_unsharing;
> > >  
> > > +  /* Return year of the source language standard version if the FE supports
> > > +     multiple versions of the standard.  */
> > > +  int (*source_language) (void);
> > > +
> > >    /* Whenever you add entries here, make sure you adjust langhooks-def.h
> > >       and langhooks.c accordingly.  */
> > >  };
> > > diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/lang-c89.c b/gcc/testsuite/gcc.dg/debug/dwarf2/lang-c89.c
> > > new file mode 100644
> > > index 0000000..6292cf8
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.dg/debug/dwarf2/lang-c89.c
> > > @@ -0,0 +1,6 @@
> > > +/* { dg-do compile } */
> > > +/* { dg-options "-O -std=c89 -g -dA" } */
> > > +/* DW_LANG_C89 = 0x0001 */
> > > +/* { dg-final { scan-assembler "0x1.*DW_AT_language" } } */
> > > +
> > > +int version;
> > > diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/lang-c99.c b/gcc/testsuite/gcc.dg/debug/dwarf2/lang-c99.c
> > > new file mode 100644
> > > index 0000000..1d789fe
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.dg/debug/dwarf2/lang-c99.c
> > > @@ -0,0 +1,6 @@
> > > +// { dg-do compile }
> > > +// { dg-options "-O -std=c99 -g -dA" }
> > > +// DW_LANG_C99 = 0x000c
> > > +// { dg-final { scan-assembler "0xc.*DW_AT_language" } } */
> > > +
> > > +int version;
> > 

	Jakub