[rfa] ENUM_BITFIELD, here it comes again

[Michael Elizabeth Chastain <mec at shout dot net>]

Here we go again ... a new version of my ENUM_BITFIELD patch.

First the good part:

  before: 99360768
  after:  90001408

This is a medium sized program (a specific build of gdb) along with a
debugging version of glibc using "gdb -readnow HEAD-gdb-old".  Then I
typed 'maint space 1'.

The major difference from the previous version is that I hoisted the
definition of 'enum minimal_symbol_type' from inside 'struct
minimal_symbol' to the top level.  This avoids trouble with gcc
warnings (gcc 3.3.1) or errors (gcc 3.2-7-rh).

Testing: as before, I ran the test suite with gcc v2 and v3,
dwarf-2 and stabs+, binutils 2.14.  Also, I tested the non-gcc case
by putting an "#if 0" into the defs.h test in order to get the
non-gcc path.

Size reduction (on my vanilla native i686-pc-linux-gnu):

  struct general_symbol_info  24  20
  struct minimal_symbol       44  40
  struct symbol               60  48
  struct partial_symbol       32  24

Jim B approved an earlier version of this patch, but then I noticed
that little enum glitch.  Sigh.

Okay to commit?

Michael C

===

2003-08-19  Michael Chastain  <mec@shout.net>

	* defs.h (ENUM_BITFIELD): New macro.
	* symtab.h (ENUM_BITFIELD): Use it.
	(BYTE_BITFIELD): Remove old macro, which was already disabled.

Index: defs.h
===================================================================
RCS file: /cvs/src/src/gdb/defs.h,v
retrieving revision 1.127
diff -u -r1.127 defs.h
--- defs.h	9 Aug 2003 14:57:30 -0000	1.127
+++ defs.h	19 Aug 2003 18:34:31 -0000
@@ -285,6 +285,15 @@
 #endif
 #endif
 
+/* Be conservative and use enum bitfields only with GCC.
+   This is copied from gcc 3.3.1, system.h.  */
+
+#if defined(__GNUC__) && (__GNUC__ >= 2)
+#define ENUM_BITFIELD(TYPE) enum TYPE
+#else
+#define ENUM_BITFIELD(TYPE) unsigned int
+#endif
+
 /* Needed for various prototypes */
 
 struct symtab;
Index: symtab.h
===================================================================
RCS file: /cvs/src/src/gdb/symtab.h,v
retrieving revision 1.77
diff -u -r1.77 symtab.h
--- symtab.h	22 Jul 2003 15:41:59 -0000	1.77
+++ symtab.h	19 Aug 2003 18:34:33 -0000
@@ -35,17 +35,6 @@
 struct axs_value;
 struct agent_expr;
 
-/* Don't do this; it means that if some .o's are compiled with GNU C
-   and some are not (easy to do accidentally the way we configure
-   things; also it is a pain to have to "make clean" every time you
-   want to switch compilers), then GDB dies a horrible death.  */
-/* GNU C supports enums that are bitfields.  Some compilers don't. */
-#if 0 && defined(__GNUC__) && !defined(BYTE_BITFIELD)
-#define	BYTE_BITFIELD	:8;
-#else
-#define	BYTE_BITFIELD		/*nothing */
-#endif
-
 /* Define a structure for the information that is common to all symbol types,
    including minimal symbols, partial symbols, and full symbols.  In a
    multilanguage environment, some language specific information may need to
@@ -107,7 +96,7 @@
      This is used to select one of the fields from the language specific
      union above. */
 
-  enum language language BYTE_BITFIELD;
+  ENUM_BITFIELD(language) language : 8;
 
   /* Which section is this symbol in?  This is an index into
      section_offsets for this objfile.  Negative means that the symbol
@@ -227,6 +216,37 @@
 #define SYMBOL_MATCHES_NATURAL_NAME(symbol, name)			\
   (strcmp_iw (SYMBOL_NATURAL_NAME (symbol), (name)) == 0)
 
+/* Classification types for this symbol.  These should be taken as "advisory
+   only", since if gdb can't easily figure out a classification it simply
+   selects mst_unknown.  It may also have to guess when it can't figure out
+   which is a better match between two types (mst_data versus mst_bss) for
+   example.  Since the minimal symbol info is sometimes derived from the
+   BFD library's view of a file, we need to live with what information bfd
+   supplies. */
+
+enum minimal_symbol_type
+{
+  mst_unknown = 0,		/* Unknown type, the default */
+  mst_text,			/* Generally executable instructions */
+  mst_data,			/* Generally initialized data */
+  mst_bss,			/* Generally uninitialized data */
+  mst_abs,			/* Generally absolute (nonrelocatable) */
+  /* GDB uses mst_solib_trampoline for the start address of a shared
+     library trampoline entry.  Breakpoints for shared library functions
+     are put there if the shared library is not yet loaded.
+     After the shared library is loaded, lookup_minimal_symbol will
+     prefer the minimal symbol from the shared library (usually
+     a mst_text symbol) over the mst_solib_trampoline symbol, and the
+     breakpoints will be moved to their true address in the shared
+     library via breakpoint_re_set.  */
+  mst_solib_trampoline,	/* Shared library trampoline code */
+  /* For the mst_file* types, the names are only guaranteed to be unique
+     within a given .o file.  */
+  mst_file_text,		/* Static version of mst_text */
+  mst_file_data,		/* Static version of mst_data */
+  mst_file_bss		/* Static version of mst_bss */
+};
+
 /* Define a simple structure used to hold some very basic information about
    all defined global symbols (text, data, bss, abs, etc).  The only required
    information is the general_symbol_info.
@@ -268,37 +288,7 @@
   char *filename;
 #endif
 
-  /* Classification types for this symbol.  These should be taken as "advisory
-     only", since if gdb can't easily figure out a classification it simply
-     selects mst_unknown.  It may also have to guess when it can't figure out
-     which is a better match between two types (mst_data versus mst_bss) for
-     example.  Since the minimal symbol info is sometimes derived from the
-     BFD library's view of a file, we need to live with what information bfd
-     supplies. */
-
-  enum minimal_symbol_type
-  {
-    mst_unknown = 0,		/* Unknown type, the default */
-    mst_text,			/* Generally executable instructions */
-    mst_data,			/* Generally initialized data */
-    mst_bss,			/* Generally uninitialized data */
-    mst_abs,			/* Generally absolute (nonrelocatable) */
-    /* GDB uses mst_solib_trampoline for the start address of a shared
-       library trampoline entry.  Breakpoints for shared library functions
-       are put there if the shared library is not yet loaded.
-       After the shared library is loaded, lookup_minimal_symbol will
-       prefer the minimal symbol from the shared library (usually
-       a mst_text symbol) over the mst_solib_trampoline symbol, and the
-       breakpoints will be moved to their true address in the shared
-       library via breakpoint_re_set.  */
-    mst_solib_trampoline,	/* Shared library trampoline code */
-    /* For the mst_file* types, the names are only guaranteed to be unique
-       within a given .o file.  */
-    mst_file_text,		/* Static version of mst_text */
-    mst_file_data,		/* Static version of mst_data */
-    mst_file_bss		/* Static version of mst_bss */
-  }
-  type BYTE_BITFIELD;
+  ENUM_BITFIELD(minimal_symbol_type) type : 8;
 
   /* Minimal symbols with the same hash key are kept on a linked
      list.  This is the link.  */
@@ -321,7 +311,7 @@
 /* Different name domains for symbols.  Looking up a symbol specifies a
    domain and ignores symbol definitions in other name domains. */
 
-typedef enum
+typedef enum domain_enum_tag
 {
   /* UNDEF_DOMAIN is used when a domain has not been discovered or
      none of the following apply.  This usually indicates an error either
@@ -578,11 +568,11 @@
 
   /* Domain code.  */
 
-  domain_enum domain BYTE_BITFIELD;
+  ENUM_BITFIELD(domain_enum_tag) domain : 6;
 
   /* Address class */
 
-  enum address_class aclass BYTE_BITFIELD;
+  ENUM_BITFIELD(address_class) aclass : 6;
 
   /* Line number of definition.  FIXME:  Should we really make the assumption
      that nobody will try to debug files longer than 64K lines?  What about
@@ -655,11 +645,11 @@
 
   /* Name space code.  */
 
-  domain_enum domain BYTE_BITFIELD;
+  ENUM_BITFIELD(domain_enum_tag) domain : 6;
 
   /* Address class (for info_symbols) */
 
-  enum address_class aclass BYTE_BITFIELD;
+  ENUM_BITFIELD(address_class) aclass : 6;
 
 };
 

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