diff mbox

Use GCC5/DWARF5 DW_AT_noreturn to mark functions that don't return normally.

Message ID 1417099980-31834-1-git-send-email-mjw@redhat.com
State New
Headers show

Commit Message

Mark Wielaard Nov. 27, 2014, 2:53 p.m. UTC
Add a flag field is_noreturn to struct func_type. Make calling_convention
a small bit field to not increase the size of the struct. Set is_noreturn
if the new GCC5/DWARF5 DW_AT_noreturn is set on a DW_TAG_subprogram.
Use this information to warn the user before doing a finish or return from
a function that does not return normally to its caller.

(gdb) finish
Warning. Function endless does not return normally.
Try to finish anyway? (y or n)

(gdb) return
warning: Function does not return normally to caller!
Make endless return now? (y or n)

gdb/ChangeLog

	* dwarf2read.c (read_subroutine_type): Set TYPE_NO_RETURN from
	DW_AT_noreturn.
	* gdbtypes.h (struct func_type): Add is_noreturn field flag. Make
	calling_convention an 8 bit bit field.
	(TYPE_NO_RETURN): New macro.
	* infcmd.c (finish_command): Query if function does not return
	normally.
	* stack.c (return_command): Likewise.

include/ChangeLog

	* dwarf2.def (DW_AT_noreturn): New DWARF5 attribute.

The dwarf2.h addition and the code to emit the new attribute is already in
the gcc tree.

OK to commit?

Thanks,

Mark

Comments

Mark Wielaard Dec. 4, 2014, 1:26 p.m. UTC | #1
On Thu, 2014-11-27 at 15:53 +0100, Mark Wielaard wrote:
> Add a flag field is_noreturn to struct func_type. Make calling_convention
> a small bit field to not increase the size of the struct. Set is_noreturn
> if the new GCC5/DWARF5 DW_AT_noreturn is set on a DW_TAG_subprogram.
> Use this information to warn the user before doing a finish or return from
> a function that does not return normally to its caller.
> 
> (gdb) finish
> Warning. Function endless does not return normally.
> Try to finish anyway? (y or n)
> 
> (gdb) return
> warning: Function does not return normally to caller!
> Make endless return now? (y or n)
> 
> gdb/ChangeLog
> 
> 	* dwarf2read.c (read_subroutine_type): Set TYPE_NO_RETURN from
> 	DW_AT_noreturn.
> 	* gdbtypes.h (struct func_type): Add is_noreturn field flag. Make
> 	calling_convention an 8 bit bit field.
> 	(TYPE_NO_RETURN): New macro.
> 	* infcmd.c (finish_command): Query if function does not return
> 	normally.
> 	* stack.c (return_command): Likewise.
> 
> include/ChangeLog
> 
> 	* dwarf2.def (DW_AT_noreturn): New DWARF5 attribute.
> 
> The dwarf2.h addition and the code to emit the new attribute is already in
> the gcc tree.
> 
> OK to commit?

Ping.

> diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
> index 36cbbd9..56212e5 100644
> --- a/gdb/dwarf2read.c
> +++ b/gdb/dwarf2read.c
> @@ -14312,6 +14312,12 @@ read_subroutine_type (struct die_info *die, struct dwarf2_cu *cu)
>    else
>      TYPE_CALLING_CONVENTION (ftype) = DW_CC_normal;
>  
> +  /* Record whether the function returns normally to its caller or not
> +     if the DWARF producer set that information.  */
> +  attr = dwarf2_attr (die, DW_AT_noreturn, cu);
> +  if (attr && (DW_UNSND (attr) != 0))
> +    TYPE_NO_RETURN (ftype) = 1;
> +
>    /* We need to add the subroutine type to the die immediately so
>       we don't infinitely recurse when dealing with parameters
>       declared as the same subroutine type.  */
> diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h
> index 14a1f08..779b728 100644
> --- a/gdb/gdbtypes.h
> +++ b/gdb/gdbtypes.h
> @@ -1019,9 +1019,16 @@ struct func_type
>    {
>      /* * The calling convention for targets supporting multiple ABIs.
>         Right now this is only fetched from the Dwarf-2
> -       DW_AT_calling_convention attribute.  */
> +       DW_AT_calling_convention attribute.  The value is one of the
> +       DW_CC enum dwarf_calling_convention constants.  */
>  
> -    unsigned calling_convention;
> +    unsigned calling_convention : 8;
> +
> +    /* * Whether this function normally returns to its caller.  It is
> +       set from the DW_AT_noreturn attribute if set on the
> +       DW_TAG_subprogram.  */
> +
> +    unsigned int is_noreturn : 1;
>  
>      /* * Only those DW_TAG_GNU_call_site's in this function that have
>         DW_AT_GNU_tail_call set are linked in this list.  Function
> @@ -1245,6 +1252,7 @@ extern void allocate_gnat_aux_type (struct type *);
>  #define TYPE_GNAT_SPECIFIC(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.gnat_stuff
>  #define TYPE_DESCRIPTIVE_TYPE(thistype) TYPE_GNAT_SPECIFIC(thistype)->descriptive_type
>  #define TYPE_CALLING_CONVENTION(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->calling_convention
> +#define TYPE_NO_RETURN(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->is_noreturn
>  #define TYPE_TAIL_CALL_LIST(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->tail_call_list
>  #define TYPE_BASECLASS(thistype,index) TYPE_FIELD_TYPE(thistype, index)
>  #define TYPE_N_BASECLASSES(thistype) TYPE_CPLUS_SPECIFIC(thistype)->n_baseclasses
> diff --git a/gdb/infcmd.c b/gdb/infcmd.c
> index 4415b31..8231306 100644
> --- a/gdb/infcmd.c
> +++ b/gdb/infcmd.c
> @@ -1869,7 +1869,14 @@ finish_command (char *arg, int from_tty)
>        if (execution_direction == EXEC_REVERSE)
>  	printf_filtered (_("Run back to call of "));
>        else
> -	printf_filtered (_("Run till exit from "));
> +	{
> +	  if (function != NULL && TYPE_NO_RETURN (function->type)
> +	      && ! query (_("Warning. Function %s does not return normally.\n"
> +			    "Try to finish anyway? "),
> +			  SYMBOL_PRINT_NAME (function)))
> +	    error (_("Not confirmed."));
> +	  printf_filtered (_("Run till exit from "));
> +	}
>  
>        print_stack_frame (get_selected_frame (NULL), 1, LOCATION, 0);
>      }
> diff --git a/gdb/stack.c b/gdb/stack.c
> index 2834801..c753005 100644
> --- a/gdb/stack.c
> +++ b/gdb/stack.c
> @@ -2462,8 +2462,12 @@ return_command (char *retval_exp, int from_tty)
>  	confirmed = query (_("%sMake selected stack frame return now? "),
>  			   query_prefix);
>        else
> -	confirmed = query (_("%sMake %s return now? "), query_prefix,
> -			   SYMBOL_PRINT_NAME (thisfun));
> +	{
> +	  if (TYPE_NO_RETURN (thisfun->type))
> +	    warning ("Function does not return normally to caller!");
> +	  confirmed = query (_("%sMake %s return now? "), query_prefix,
> +			     SYMBOL_PRINT_NAME (thisfun));
> +	}
>        if (!confirmed)
>  	error (_("Not confirmed"));
>      }
> diff --git a/include/dwarf2.def b/include/dwarf2.def
> index 8ca143c..8533a3e 100644
> --- a/include/dwarf2.def
> +++ b/include/dwarf2.def
> @@ -308,6 +308,8 @@ DW_AT (DW_AT_data_bit_offset, 0x6b)
>  DW_AT (DW_AT_const_expr, 0x6c)
>  DW_AT (DW_AT_enum_class, 0x6d)
>  DW_AT (DW_AT_linkage_name, 0x6e)
> +/* DWARF 5.  */
> +DW_AT (DW_AT_noreturn, 0x87)
>  
>  DW_AT_DUP (DW_AT_lo_user, 0x2000) /* Implementation-defined range start.  */
>  DW_AT_DUP (DW_AT_hi_user, 0x3fff) /* Implementation-defined range end.  */
>
Pedro Alves Dec. 4, 2014, 2:02 p.m. UTC | #2
Hi Mark,

Thanks for doing this.

On 11/27/2014 02:53 PM, Mark Wielaard wrote:
> Add a flag field is_noreturn to struct func_type. Make calling_convention
> a small bit field to not increase the size of the struct. Set is_noreturn
> if the new GCC5/DWARF5 DW_AT_noreturn is set on a DW_TAG_subprogram.
> Use this information to warn the user before doing a finish or return from
> a function that does not return normally to its caller.
> 
> (gdb) finish
> Warning. Function endless does not return normally.
> Try to finish anyway? (y or n)
> 
> (gdb) return
> warning: Function does not return normally to caller!
> Make endless return now? (y or n)

I'd suggest making the warnings a bit more consistent.

- "Warning." vs "warning: "

  Prefer the latter, as that's what the "warning" function uses.

- "." vs "!"

  I'd keep it calm and get rid of the "!".  :-)

> 
> gdb/ChangeLog
> 
> 	* dwarf2read.c (read_subroutine_type): Set TYPE_NO_RETURN from
> 	DW_AT_noreturn.
> 	* gdbtypes.h (struct func_type): Add is_noreturn field flag. Make
> 	calling_convention an 8 bit bit field.
> 	(TYPE_NO_RETURN): New macro.
> 	* infcmd.c (finish_command): Query if function does not return
> 	normally.
> 	* stack.c (return_command): Likewise.
> 
> include/ChangeLog
> 
> 	* dwarf2.def (DW_AT_noreturn): New DWARF5 attribute.

I wonder if we could have a test?  Could e.g., make sure we don't
crash when the user confirms a return in a noreturn function.

> diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
> index 36cbbd9..56212e5 100644
> --- a/gdb/dwarf2read.c
> +++ b/gdb/dwarf2read.c
> @@ -14312,6 +14312,12 @@ read_subroutine_type (struct die_info *die, struct dwarf2_cu *cu)
>    else
>      TYPE_CALLING_CONVENTION (ftype) = DW_CC_normal;
>  
> +  /* Record whether the function returns normally to its caller or not
> +     if the DWARF producer set that information.  */
> +  attr = dwarf2_attr (die, DW_AT_noreturn, cu);
> +  if (attr && (DW_UNSND (attr) != 0))

 if (attr != NULL && (DW_UNSND (attr) != 0))

> +    TYPE_NO_RETURN (ftype) = 1;
> +
>    /* We need to add the subroutine type to the die immediately so
>       we don't infinitely recurse when dealing with parameters
>       declared as the same subroutine type.  */



> --- a/gdb/infcmd.c
> +++ b/gdb/infcmd.c
> @@ -1869,7 +1869,14 @@ finish_command (char *arg, int from_tty)
>        if (execution_direction == EXEC_REVERSE)
>  	printf_filtered (_("Run back to call of "));
>        else
> -	printf_filtered (_("Run till exit from "));
> +	{
> +	  if (function != NULL && TYPE_NO_RETURN (function->type)
> +	      && ! query (_("Warning. Function %s does not return normally.\n"
> +			    "Try to finish anyway? "),
> +			  SYMBOL_PRINT_NAME (function)))
> +	    error (_("Not confirmed."));
> +	  printf_filtered (_("Run till exit from "));
> +	}

No space between "!" and query:

	      && !query ...

> --- a/gdb/stack.c
> +++ b/gdb/stack.c
> @@ -2462,8 +2462,12 @@ return_command (char *retval_exp, int from_tty)
>  	confirmed = query (_("%sMake selected stack frame return now? "),
>  			   query_prefix);
>        else
> -	confirmed = query (_("%sMake %s return now? "), query_prefix,
> -			   SYMBOL_PRINT_NAME (thisfun));
> +	{
> +	  if (TYPE_NO_RETURN (thisfun->type))
> +	    warning ("Function does not return normally to caller!");

i18n / _() .

Thanks,
Pedro Alves
diff mbox

Patch

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 36cbbd9..56212e5 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -14312,6 +14312,12 @@  read_subroutine_type (struct die_info *die, struct dwarf2_cu *cu)
   else
     TYPE_CALLING_CONVENTION (ftype) = DW_CC_normal;
 
+  /* Record whether the function returns normally to its caller or not
+     if the DWARF producer set that information.  */
+  attr = dwarf2_attr (die, DW_AT_noreturn, cu);
+  if (attr && (DW_UNSND (attr) != 0))
+    TYPE_NO_RETURN (ftype) = 1;
+
   /* We need to add the subroutine type to the die immediately so
      we don't infinitely recurse when dealing with parameters
      declared as the same subroutine type.  */
diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h
index 14a1f08..779b728 100644
--- a/gdb/gdbtypes.h
+++ b/gdb/gdbtypes.h
@@ -1019,9 +1019,16 @@  struct func_type
   {
     /* * The calling convention for targets supporting multiple ABIs.
        Right now this is only fetched from the Dwarf-2
-       DW_AT_calling_convention attribute.  */
+       DW_AT_calling_convention attribute.  The value is one of the
+       DW_CC enum dwarf_calling_convention constants.  */
 
-    unsigned calling_convention;
+    unsigned calling_convention : 8;
+
+    /* * Whether this function normally returns to its caller.  It is
+       set from the DW_AT_noreturn attribute if set on the
+       DW_TAG_subprogram.  */
+
+    unsigned int is_noreturn : 1;
 
     /* * Only those DW_TAG_GNU_call_site's in this function that have
        DW_AT_GNU_tail_call set are linked in this list.  Function
@@ -1245,6 +1252,7 @@  extern void allocate_gnat_aux_type (struct type *);
 #define TYPE_GNAT_SPECIFIC(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.gnat_stuff
 #define TYPE_DESCRIPTIVE_TYPE(thistype) TYPE_GNAT_SPECIFIC(thistype)->descriptive_type
 #define TYPE_CALLING_CONVENTION(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->calling_convention
+#define TYPE_NO_RETURN(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->is_noreturn
 #define TYPE_TAIL_CALL_LIST(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->tail_call_list
 #define TYPE_BASECLASS(thistype,index) TYPE_FIELD_TYPE(thistype, index)
 #define TYPE_N_BASECLASSES(thistype) TYPE_CPLUS_SPECIFIC(thistype)->n_baseclasses
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 4415b31..8231306 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -1869,7 +1869,14 @@  finish_command (char *arg, int from_tty)
       if (execution_direction == EXEC_REVERSE)
 	printf_filtered (_("Run back to call of "));
       else
-	printf_filtered (_("Run till exit from "));
+	{
+	  if (function != NULL && TYPE_NO_RETURN (function->type)
+	      && ! query (_("Warning. Function %s does not return normally.\n"
+			    "Try to finish anyway? "),
+			  SYMBOL_PRINT_NAME (function)))
+	    error (_("Not confirmed."));
+	  printf_filtered (_("Run till exit from "));
+	}
 
       print_stack_frame (get_selected_frame (NULL), 1, LOCATION, 0);
     }
diff --git a/gdb/stack.c b/gdb/stack.c
index 2834801..c753005 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -2462,8 +2462,12 @@  return_command (char *retval_exp, int from_tty)
 	confirmed = query (_("%sMake selected stack frame return now? "),
 			   query_prefix);
       else
-	confirmed = query (_("%sMake %s return now? "), query_prefix,
-			   SYMBOL_PRINT_NAME (thisfun));
+	{
+	  if (TYPE_NO_RETURN (thisfun->type))
+	    warning ("Function does not return normally to caller!");
+	  confirmed = query (_("%sMake %s return now? "), query_prefix,
+			     SYMBOL_PRINT_NAME (thisfun));
+	}
       if (!confirmed)
 	error (_("Not confirmed"));
     }
diff --git a/include/dwarf2.def b/include/dwarf2.def
index 8ca143c..8533a3e 100644
--- a/include/dwarf2.def
+++ b/include/dwarf2.def
@@ -308,6 +308,8 @@  DW_AT (DW_AT_data_bit_offset, 0x6b)
 DW_AT (DW_AT_const_expr, 0x6c)
 DW_AT (DW_AT_enum_class, 0x6d)
 DW_AT (DW_AT_linkage_name, 0x6e)
+/* DWARF 5.  */
+DW_AT (DW_AT_noreturn, 0x87)
 
 DW_AT_DUP (DW_AT_lo_user, 0x2000) /* Implementation-defined range start.  */
 DW_AT_DUP (DW_AT_hi_user, 0x3fff) /* Implementation-defined range end.  */