[RFC] Remove cleanups from coffread.c

  This removes the remaining cleanups from coffread.c.

Tested by the buildbot.  However, I don't think the buildbot really
tests these code paths, and TBH I am not sure how to do it manually.
I did manage to crash an earlier version of the patch using a mingw
.exe file, though I would have thought that was only going to test
coff-pe-read.c.

gdb/ChangeLog
2018-11-05  Tom Tromey  <tom@tromey.com>

	* stabsread.h (struct stab_section_list): Remove.
	(coffstab_build_psymtabs): Update.
	* dbxread.c (symbuf_sections): Now a std::vector.
	(sect_idx): New global.
	(fill_symbuf): Update.
	(coffstab_build_psymtabs): Change type of stabsects parameter.
	Update.
	* coffread.c (struct coff_symfile_info) <stabsects>: Now a
	std::vector.
	(linetab, linetab_offset, linetab_size, stringtab): Move earlier.
	(coff_locate_sections): Update.
	(coff_symfile_read): Remove cleanups.  Update.
	(init_stringtab): Add storage parameter.
	(free_stringtab, free_stringtab_cleanup): Remove.
	(init_lineno): Add storage parameter.
	(free_linetab, free_linetab_cleanup): Remove.
---
 gdb/ChangeLog   |  19 ++++++++
 gdb/coffread.c  | 113 ++++++++++++++----------------------------------
 gdb/dbxread.c   |  32 +++++++-------
 gdb/stabsread.h |  14 +-----
 4 files changed, 70 insertions(+), 108 deletions(-)
  

Hi Tom,

> This removes the remaining cleanups from coffread.c.
> 
> Tested by the buildbot.  However, I don't think the buildbot really
> tests these code paths, and TBH I am not sure how to do it manually.
> I did manage to crash an earlier version of the patch using a mingw
> .exe file, though I would have thought that was only going to test
> coff-pe-read.c.
> 
> gdb/ChangeLog
> 2018-11-05  Tom Tromey  <tom@tromey.com>
> 
> 	* stabsread.h (struct stab_section_list): Remove.
> 	(coffstab_build_psymtabs): Update.
> 	* dbxread.c (symbuf_sections): Now a std::vector.
> 	(sect_idx): New global.
> 	(fill_symbuf): Update.
> 	(coffstab_build_psymtabs): Change type of stabsects parameter.
> 	Update.
> 	* coffread.c (struct coff_symfile_info) <stabsects>: Now a
> 	std::vector.
> 	(linetab, linetab_offset, linetab_size, stringtab): Move earlier.
> 	(coff_locate_sections): Update.
> 	(coff_symfile_read): Remove cleanups.  Update.
> 	(init_stringtab): Add storage parameter.
> 	(free_stringtab, free_stringtab_cleanup): Remove.
> 	(init_lineno): Add storage parameter.
> 	(free_linetab, free_linetab_cleanup): Remove.

First of all, thanks for the patch!

I've been meaning to try to review this patch since you posted it,
and unfortunately I haven't had the time. So I decided to at least
give it a quick test -- hoping it would only take a few minutes and
still be better than nothing.  And unfortunately, it seems to be causing
some regressions. With a simple program, we can see:

    $ gdb -q --nh simple_main.exe
    Reading symbols from simple_main.exe...
    The debugging information in `C:\tmp\brobecke\ex\simple\simple_main.exe' is corrupted.
    The file has a `.stabs' section, but no `.stabstr' section.
    (gdb) run
    Starting program: C:\tmp\gdb-TS-kdpzkw\simple\simple_main.exe
    Error while reading shared library symbols for C:\Windows\SYSTEM32\ntdll.dll:
    The debugging information in `C:\Windows\SYSTEM32\ntdll.dll' is corrupted.
    The file has a `.stabs' section, but no `.stabstr' section.
    Error while reading shared library symbols for C:\Windows\System32\kernel32.dll:
    The debugging information in `C:\Windows\System32\kernel32.dll' is corrupted.
    The file has a `.stabs' section, but no `.stabstr' section.
    [etc]

I'll keep this one in my list to investigate further when I have
a moment; Looking at the error message, I don't think it is necessarily
very complicated, but I probably won't have time before mid December :-(.


> ---
>  gdb/ChangeLog   |  19 ++++++++
>  gdb/coffread.c  | 113 ++++++++++++++----------------------------------
>  gdb/dbxread.c   |  32 +++++++-------
>  gdb/stabsread.h |  14 +-----
>  4 files changed, 70 insertions(+), 108 deletions(-)
> 
> diff --git a/gdb/coffread.c b/gdb/coffread.c
> index a473b78245..4feb449948 100644
> --- a/gdb/coffread.c
> +++ b/gdb/coffread.c
> @@ -58,7 +58,7 @@ struct coff_symfile_info
>  
>      CORE_ADDR textaddr;		/* Addr of .text section.  */
>      unsigned int textsize;	/* Size of .text section.  */
> -    struct stab_section_list *stabsects;	/* .stab sections.  */
> +    std::vector<asection *> *stabsects;	/* .stab sections.  */
>      asection *stabstrsect;	/* Section pointer for .stab section.  */
>      char *stabstrdata;
>    };
> @@ -155,6 +155,12 @@ static int type_vector_length;
>  
>  #define INITIAL_TYPE_VECTOR_LENGTH 160
>  
> +static char *linetab = NULL;
> +static long linetab_offset;
> +static unsigned long linetab_size;
> +
> +static char *stringtab = NULL;
> +
>  extern void stabsread_clear_cache (void);
>  
>  static struct type *coff_read_struct_type (int, int, int,
> @@ -185,21 +191,13 @@ static void patch_opaque_types (struct symtab *);
>  
>  static void enter_linenos (long, int, int, struct objfile *);
>  
> -static void free_linetab (void);
> -
> -static void free_linetab_cleanup (void *ignore);
> -
> -static int init_lineno (bfd *, long, int);
> +static int init_lineno (bfd *, long, int, gdb::unique_xmalloc_ptr<char> *);
>  
>  static char *getsymname (struct internal_syment *);
>  
>  static const char *coff_getfilename (union internal_auxent *);
>  
> -static void free_stringtab (void);
> -
> -static void free_stringtab_cleanup (void *ignore);
> -
> -static int init_stringtab (bfd *, long);
> +static int init_stringtab (bfd *, long, gdb::unique_xmalloc_ptr<char> *);
>  
>  static void read_one_sym (struct coff_symbol *,
>  			  struct internal_syment *,
> @@ -249,21 +247,7 @@ coff_locate_sections (bfd *abfd, asection *sectp, void *csip)
>  	if (!isdigit (*s))
>  	  break;
>        if (*s == '\0')
> -	{
> -	  struct stab_section_list *n, **pn;
> -
> -	  n = XNEW (struct stab_section_list);
> -	  n->section = sectp;
> -	  n->next = NULL;
> -	  for (pn = &csi->stabsects; *pn != NULL; pn = &(*pn)->next)
> -	    ;
> -	  *pn = n;
> -
> -	  /* This will be run after coffstab_build_psymtabs is called
> -	     in coff_symfile_read, at which point we no longer need
> -	     the information.  */
> -	  make_cleanup (xfree, n);
> -	}
> +	csi->stabsects->push_back (sectp);
>      }
>  }
>  
> @@ -570,13 +554,16 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
>    unsigned int num_symbols;
>    int symtab_offset;
>    int stringtab_offset;
> -  struct cleanup *back_to;
>    int stabstrsize;
>    
>    info = (struct coff_symfile_info *) objfile_data (objfile,
>  						    coff_objfile_data_key);
>    symfile_bfd = abfd;		/* Kludge for swap routines.  */
>  
> +  std::vector<asection *> stabsects;
> +  scoped_restore restore_stabsects
> +    = make_scoped_restore (&info->stabsects, &stabsects);
> +
>  /* WARNING WILL ROBINSON!  ACCESSING BFD-PRIVATE DATA HERE!  FIXME!  */
>    num_symbols = bfd_get_symcount (abfd);	/* How many syms */
>    symtab_offset = cdata->sym_filepos;	/* Symbol table file offset */
> @@ -595,10 +582,10 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
>  
>    /* Allocate space for raw symbol and aux entries, based on their
>       space requirements as reported by BFD.  */
> -  temp_sym = (char *) xmalloc
> -    (cdata->local_symesz + cdata->local_auxesz);
> +  gdb::def_vector<char> temp_storage (cdata->local_symesz
> +				      + cdata->local_auxesz);
> +  temp_sym = temp_storage.data ();
>    temp_aux = temp_sym + cdata->local_symesz;
> -  back_to = make_cleanup (free_current_contents, &temp_sym);
>  
>    /* We need to know whether this is a PE file, because in PE files,
>       unlike standard COFF files, symbol values are stored as offsets
> @@ -628,22 +615,25 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
>       can avoid spurious error messages (and maybe run a little
>       faster!) by not even reading the line number table unless we have
>       symbols.  */
> +  scoped_restore restore_linetab = make_scoped_restore (&linetab);
> +  gdb::unique_xmalloc_ptr<char> linetab_storage;
>    if (num_symbols > 0)
>      {
>        /* Read the line number table, all at once.  */
>        bfd_map_over_sections (abfd, find_linenos, (void *) info);
>  
> -      make_cleanup (free_linetab_cleanup, 0 /*ignore*/);
>        val = init_lineno (abfd, info->min_lineno_offset,
> -                         info->max_lineno_offset - info->min_lineno_offset);
> +                         info->max_lineno_offset - info->min_lineno_offset,
> +			 &linetab_storage);
>        if (val < 0)
>          error (_("\"%s\": error reading line numbers."), filename);
>      }
>  
>    /* Now read the string table, all at once.  */
>  
> -  make_cleanup (free_stringtab_cleanup, 0 /*ignore*/);
> -  val = init_stringtab (abfd, stringtab_offset);
> +  scoped_restore restore_stringtab = make_scoped_restore (&stringtab);
> +  gdb::unique_xmalloc_ptr<char> stringtab_storage;
> +  val = init_stringtab (abfd, stringtab_offset, &stringtab_storage);
>    if (val < 0)
>      error (_("\"%s\": can't get string table"), filename);
>  
> @@ -720,7 +710,7 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
>  
>        coffstab_build_psymtabs (objfile,
>  			       info->textaddr, info->textsize,
> -			       info->stabsects,
> +			       *info->stabsects,
>  			       info->stabstrsect->filepos, stabstrsize);
>      }
>    if (dwarf2_has_info (objfile, NULL))
> @@ -747,8 +737,6 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
>  				    symfile_flags, objfile);
>  	}
>      }
> -
> -  do_cleanups (back_to);
>  }
>  
>  static void
> @@ -1298,17 +1286,13 @@ read_one_sym (struct coff_symbol *cs,
>  
>  /* Support for string table handling.  */
>  
> -static char *stringtab = NULL;
> -
>  static int
> -init_stringtab (bfd *abfd, long offset)
> +init_stringtab (bfd *abfd, long offset, gdb::unique_xmalloc_ptr<char> *storage)
>  {
>    long length;
>    int val;
>    unsigned char lengthbuf[4];
>  
> -  free_stringtab ();
> -
>    /* If the file is stripped, the offset might be zero, indicating no
>       string table.  Just return with `stringtab' set to null.  */
>    if (offset == 0)
> @@ -1325,7 +1309,8 @@ init_stringtab (bfd *abfd, long offset)
>    if (val != sizeof lengthbuf || length < sizeof lengthbuf)
>      return 0;
>  
> -  stringtab = (char *) xmalloc (length);
> +  storage->reset ((char *) xmalloc (length));
> +  stringtab = storage->get ();
>    /* This is in target format (probably not very useful, and not
>       currently used), not host format.  */
>    memcpy (stringtab, lengthbuf, sizeof lengthbuf);
> @@ -1340,20 +1325,6 @@ init_stringtab (bfd *abfd, long offset)
>    return 0;
>  }
>  
> -static void
> -free_stringtab (void)
> -{
> -  if (stringtab)
> -    xfree (stringtab);
> -  stringtab = NULL;
> -}
> -
> -static void
> -free_stringtab_cleanup (void *ignore)
> -{
> -  free_stringtab ();
> -}
> -
>  static char *
>  getsymname (struct internal_syment *symbol_entry)
>  {
> @@ -1407,24 +1378,19 @@ coff_getfilename (union internal_auxent *aux_entry)
>  
>  /* Support for line number handling.  */
>  
> -static char *linetab = NULL;
> -static long linetab_offset;
> -static unsigned long linetab_size;
> -
>  /* Read in all the line numbers for fast lookups later.  Leave them in
>     external (unswapped) format in memory; we'll swap them as we enter
>     them into GDB's data structures.  */
>  
>  static int
> -init_lineno (bfd *abfd, long offset, int size)
> +init_lineno (bfd *abfd, long offset, int size,
> +	     gdb::unique_xmalloc_ptr<char> *storage)
>  {
>    int val;
>  
>    linetab_offset = offset;
>    linetab_size = size;
>  
> -  free_linetab ();
> -
>    if (size == 0)
>      return 0;
>  
> @@ -1432,9 +1398,10 @@ init_lineno (bfd *abfd, long offset, int size)
>      return -1;
>  
>    /* Allocate the desired table, plus a sentinel.  */
> -  linetab = (char *) xmalloc (size + local_linesz);
> +  storage->reset ((char *) xmalloc (size + local_linesz));
> +  linetab = storage->get ();
>  
> -  val = bfd_bread (linetab, size, abfd);
> +  val = bfd_bread (storage->get (), size, abfd);
>    if (val != size)
>      return -1;
>  
> @@ -1444,20 +1411,6 @@ init_lineno (bfd *abfd, long offset, int size)
>    return 0;
>  }
>  
> -static void
> -free_linetab (void)
> -{
> -  if (linetab)
> -    xfree (linetab);
> -  linetab = NULL;
> -}
> -
> -static void
> -free_linetab_cleanup (void *ignore)
> -{
> -  free_linetab ();
> -}
> -
>  #if !defined (L_LNNO32)
>  #define L_LNNO32(lp) ((lp)->l_lnno)
>  #endif
> diff --git a/gdb/dbxread.c b/gdb/dbxread.c
> index e004e8cb93..d2357c8c10 100644
> --- a/gdb/dbxread.c
> +++ b/gdb/dbxread.c
> @@ -751,7 +751,8 @@ static char *stringtab_global;
>  /* These variables are used to control fill_symbuf when the stabs
>     symbols are not contiguous (as may be the case when a COFF file is
>     linked using --split-by-reloc).  */
> -static struct stab_section_list *symbuf_sections;
> +static const std::vector<asection *> *symbuf_sections;
> +static size_t sect_idx;
>  static unsigned int symbuf_left;
>  static unsigned int symbuf_read;
>  
> @@ -787,13 +788,13 @@ fill_symbuf (bfd *sym_bfd)
>      {
>        if (symbuf_left <= 0)
>  	{
> -	  file_ptr filepos = symbuf_sections->section->filepos;
> +	  file_ptr filepos = (*symbuf_sections)[sect_idx]->filepos;
>  
>  	  if (bfd_seek (sym_bfd, filepos, SEEK_SET) != 0)
>  	    perror_with_name (bfd_get_filename (sym_bfd));
> -	  symbuf_left = bfd_section_size (sym_bfd, symbuf_sections->section);
> +	  symbuf_left = bfd_section_size (sym_bfd, (*symbuf_sections)[sect_idx]);
>  	  symbol_table_offset = filepos - symbuf_read;
> -	  symbuf_sections = symbuf_sections->next;
> +	  ++sect_idx;
>  	}
>  
>        count = symbuf_left;
> @@ -2962,7 +2963,7 @@ process_one_symbol (int type, int desc, CORE_ADDR valu, const char *name,
>  void
>  coffstab_build_psymtabs (struct objfile *objfile,
>  			 CORE_ADDR textaddr, unsigned int textsize,
> -			 struct stab_section_list *stabsects,
> +			 const std::vector<asection *> &stabsects,
>  			 file_ptr stabstroffset, unsigned int stabstrsize)
>  {
>    int val;
> @@ -3001,27 +3002,28 @@ coffstab_build_psymtabs (struct objfile *objfile,
>    /* In a coff file, we've already installed the minimal symbols that came
>       from the coff (non-stab) symbol table, so always act like an
>       incremental load here.  */
> -  if (stabsects->next == NULL)
> +  scoped_restore save_symbuf_sections
> +    = make_scoped_restore (&symbuf_sections);
> +  if (stabsects.size () == 1)
>      {
> -      stabsize = bfd_section_size (sym_bfd, stabsects->section);
> +      stabsize = bfd_section_size (sym_bfd, stabsects[0]);
>        DBX_SYMCOUNT (objfile) = stabsize / DBX_SYMBOL_SIZE (objfile);
> -      DBX_SYMTAB_OFFSET (objfile) = stabsects->section->filepos;
> +      DBX_SYMTAB_OFFSET (objfile) = stabsects[0]->filepos;
>      }
>    else
>      {
> -      struct stab_section_list *stabsect;
> -
>        DBX_SYMCOUNT (objfile) = 0;
> -      for (stabsect = stabsects; stabsect != NULL; stabsect = stabsect->next)
> +      for (asection *section : stabsects)
>  	{
> -	  stabsize = bfd_section_size (sym_bfd, stabsect->section);
> +	  stabsize = bfd_section_size (sym_bfd, section);
>  	  DBX_SYMCOUNT (objfile) += stabsize / DBX_SYMBOL_SIZE (objfile);
>  	}
>  
> -      DBX_SYMTAB_OFFSET (objfile) = stabsects->section->filepos;
> +      DBX_SYMTAB_OFFSET (objfile) = stabsects[0]->filepos;
>  
> -      symbuf_sections = stabsects->next;
> -      symbuf_left = bfd_section_size (sym_bfd, stabsects->section);
> +      sect_idx = 1;
> +      symbuf_sections = &stabsects;
> +      symbuf_left = bfd_section_size (sym_bfd, stabsects[0]);
>        symbuf_read = 0;
>      }
>  
> diff --git a/gdb/stabsread.h b/gdb/stabsread.h
> index b0194e0c69..3376f9eaaf 100644
> --- a/gdb/stabsread.h
> +++ b/gdb/stabsread.h
> @@ -173,18 +173,6 @@ extern void end_stabs (void);
>  
>  extern void finish_global_stabs (struct objfile *objfile);
>  
> -/* COFF files can have multiple .stab sections, if they are linked
> -   using --split-by-reloc.  This linked list is used to pass the
> -   information into the functions in dbxread.c.  */
> -struct stab_section_list
> -  {
> -    /* Next in list.  */
> -    struct stab_section_list *next;
> -
> -    /* Stab section.  */
> -    asection *section;
> -  };
> -
>  /* Functions exported by dbxread.c.  These are not in stabsread.c because
>     they are only used by some stabs readers.  */
>  
> @@ -207,7 +195,7 @@ extern void elfstab_build_psymtabs (struct objfile *objfile,
>  extern void coffstab_build_psymtabs
>    (struct objfile *objfile,
>     CORE_ADDR textaddr, unsigned int textsize,
> -   struct stab_section_list *stabs,
> +   const std::vector<asection *> &stabs,
>     file_ptr stabstroffset, unsigned int stabstrsize);
>  
>  extern void stabsect_build_psymtabs (struct objfile *objfile, char *stab_name,
> -- 
> 2.17.2