Re: [RFC] convert a host address to a string

["Kai Tietz" <ktietz70@googlemail.com>]

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2009/1/10 Joel Brobecker <brobecker@adacore.com>:
>> I think it is a sub-optimal solution to have just support for Vista64, but
>> not for XP.
>
> To me, the question is not about whether to support XP64 or not.
> I agree it would be nice to support XP64 as well.  It's about who
> has the time and energy to drive the discussion to find an accepted
> solution.  I decided to drop XP64, because it's not in the list of
> things I'm interested in while I'm sensing that it's going to take
> a bit of effort to reach a consensus. You already made a very nice
> contribution in the coff/pe reader, why not send another patch to
> further improve host_address_to_string for XP64?
>
>> On a second thought, I remembered, that bfd does things right ;) There
>> is the macro sprintf_vma in bfd.h, which handles things pretty well
>> and can be used here in utils.c, too.
>
> The problem with that routine is that it is designed to print target
> addresses, not host addresses.
>
> --
> Joel
>

ok, so I sugget the following patch instead. It is able to generate
addresses for XP64 without the use of any vendor specific printf
formatters, and uses for targets where sizeof(long) == sizeof(void*)
the long variant.

Cheers,
Kai


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Index: src/gdb/utils.c
===================================================================
--- src.orig/gdb/utils.c
+++ src/gdb/utils.c
@@ -3071,11 +3071,54 @@ host_address_to_string (const void *addr
 {
   char *str = get_cell ();
 
-  /* We could use the %p conversion specifier to sprintf if we had any
-     way of knowing whether this host supports it.  But the following
-     should work on the Alpha and on 32 bit machines.  */
-  sprintf (str, "0x%lx", (unsigned long) addr);
+  /* We do not use the %p conversion specifier, because the resulting
+     image can vary from implementation to implementation.  For instance,
+     some implementations format the pointer value with a leading "0x"
+     whereas others don't (Solaris, for instance).  Also, it is unspecified
+     whether the alphabetical digits are printed using uppercase letters
+     or not (in GDB, we want lowercase).
+
+     So we use the %x type instead.  This, however, introduces
+     a couple of issues:
+
+       1. The %x type expects an integer value, not a pointer.
+          So we first need to cast our pointer to an integer type
+          whose size is identical to the size of our pointer.
+          We use uintptr_t for that.
+
+       2. The %x type alone expects and int, which is not always
+          large enough to hold an address.  Usually, type "long"
+          has the same size as pointers, but certain ABIs define
+          the size of pointers to be larger than the size of long
+          (64bit Windows is one such example).
+
+          So, to be certain to have a type that's large enough
+          to hold an address, we need to use "long long".  But
+          the trick is that not all printf implementations support
+          the "ll" modifier.  On those platforms where the "ll"
+          modifier is not available, we'll assume that type "long"
+          can be used to print an address.
+
+          To make sure that the type we pass to sprintf matches
+          the type we specified in our expression, we perform
+          a second cast to "unsigned long long" if we used "%llx",
+          or "unsigned long" if we used "%lx".  */
+
+#if defined(PRINTF_HAS_LONG_LONG) && BITSIZEOF_SIZE_T == 64 && \
+  SIZEOF_LONG == 4
+  sprintf (str, "0x%llx", (unsigned long long) (uintptr_t) addr);
+#elif BITSIZEOF_SIZE_T == 64 && SIZEOF_LONG == 4
+  unsigned long long val = (unsigned long) (uintptr_t) addr;
+  if ((val & ~0xffffffffull) != 0)
+    sprintf (str, "0x%lx%08lx",
+             (unsigned long) (val >> 32), (unsigned long) val);
+  else
+    sprintf (str, "0x%lx", (unsigned long) (uintptr_t) val);
+#else
+  sprintf (str, "0x%lx", (unsigned long) (uintptr_t) addr);
+#endif
   return str;
+  BITSIZEOF_SIZE_T SIZEOF_LONG
 }
 
 char *