[RFA] stabs: remember types that cross reference another type

Joel Brobecker brobecker@gnat.com
Mon Nov 3 22:59:00 GMT 2003

[Rhaaaa, resending, with the patch this time. Thanks Daniel!]


We encountered the following problem when using GNAT to compile
the following pasted at the end of this message. Sorry the program
is in Ada instead of C, but I couldn't reproduce it with C.

The problem is when the user tries to print the type of My_Str.
GDB should return a string, but instead we got:

        Attempt to take contents of a non-pointer value

After investigating, I found that the stabs generated by the compiler
contained the following entries:

        .stabs "s5:(0,97)=xsstring___XUP:",128,0,5,-476
        .stabs "R6b:(0,97)",128,0,12,-484

(R6b is a variable that GDB ends up using in place of My_Str for reasons
that are related to the encoding used by GNAT).

So when GDB reads the type information for R6b, it finds that it is
of type number (0,97), which should mean the same type as s5.
Unfortunately, GDB forgot to save a reference to the type associated
to type (0,97) in the type_vector when processing the type of variable
named "s5". So later on, when GDB tries to compute the type of "R6b",
it doesn't find type (0,97) and therefore assumes it will be defined
later, and hence creates a empty type object which it hopes will be 
filled in later.

As a consequence, when the ada mode tries to print the type of R6b,
it trips over the unexpected symbol type code, and bails out with
the error message above.

The attached patch fixes this particular case.

2003-10-31  J. Brobecker  <brobecker@gnat.com>

        * stabsread.c (read_type): Save a reference to types that are defined
        as cross references to other types.

Tested on x86-linux, no regression.

Ok to apply?


with Ada.Strings.Unbounded;

procedure Parse is
   type String_Ptr is access String;
   S5 : String_Ptr := new String'("Hello");

   function Foos return String is
      return "string";
   end Foos;

   My_Str : String := Foos;

   Ustring : Ada.Strings.Unbounded.Unbounded_String;  -- STOP

end Parse;

-------------- next part --------------
Index: stabsread.c
RCS file: /cvs/src/src/gdb/stabsread.c,v
retrieving revision 1.65
diff -u -p -r1.65 stabsread.c
--- stabsread.c	6 Oct 2003 19:27:12 -0000	1.65
+++ stabsread.c	3 Nov 2003 22:58:09 -0000
@@ -1852,6 +1852,8 @@ again:
 		  obstack_free (&objfile->type_obstack, type_name);
 		  type = SYMBOL_TYPE (sym);
+	          if (typenums[0] != -1)
+	            *dbx_lookup_type (typenums) = type;
 		  return type;

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