Re: [PATCH][Middle-end]79538 missing -Wformat-overflow with %s and non-member array arguments

[Richard Biener <richard dot guenther at gmail dot com>]

On Mon, Dec 4, 2017 at 4:34 PM, Qing Zhao <qing.zhao@oracle.com> wrote:
> Hi,
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79538 <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79538>
> missing -Wformat-overflow with %s and non-member array arguments
>
> -Wformat-overflow uses the routine "get_range_strlen" to decide the
> maximum string length, however, currently "get_range_strlen" misses
> the handling of non-member arrays.
>
> Adding the handling of non-member array resolves the issue.
> Adding test case pr79538.c into gcc.dg.
>
> During gcc bootstrap, 2 source files (c-family/c-cppbuiltin.c,
> fortran/class.c) were detected new warnings by -Wformat-overflow
> due to the new handling of non-member array in "get_range_strlen".
> in order to avoid these new warnings and continue with bootstrap,
> updating these 2 files to avoid the warnings.
>
> in c-family/c-cppbuiltin.c, the warning is following:
>
> ../../latest_gcc_2/gcc/c-family/c-cppbuiltin.c:1627:15: note:
> ‘sprintf’ output 2 or more bytes (assuming 257) into a destination
> of size 256
>       sprintf (buf1, "%s=%s", macro, buf2);
>       ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> in the above, buf1 and buf2 are declared as:
> char buf1[256], buf2[256];
>
> i.e, buf1 and buf2 have same size. adjusting the size of buf1 and
> buf2 resolves the warning.
>
> fortran/class.c has the similar issue as above. Instead of adjusting
> size of the buffers, replacing sprintf with xasprintf.
>
> bootstraped and tested on both X86 and aarch64. no regression.
>
> Okay for trunk?
>
> thanks.
>
> Qing
>
> ===========================================================
>
> gcc/ChangeLog
>
> 2017-11-30  Qing Zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>
>
>       PR middle_end/79538
>       * gimple-fold.c (get_range_strlen): Add the handling of non-member array.
>
> gcc/fortran/ChangeLog
>
> 2017-11-30  Qing Zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>
>
>        PR middle_end/79538
>        * class.c (gfc_build_class_symbol): Replace call to
>        sprintf with xasprintf to avoid format-overflow warning.
>        (generate_finalization_wrapper): Likewise.
>        (gfc_find_derived_vtab): Likewise.
>        (find_intrinsic_vtab): Likewise.
>
>
> gcc/c-family/ChangeLog
>
> 2017-11-30  Qing Zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>
>
>       PR middle_end/79538
>         * c-cppbuiltin.c (builtin_define_with_hex_fp_value):
>       Adjust the size of buf1 and buf2, add a new buf to avoid
>       format-overflow warning.
>
> gcc/testsuite/ChangeLog
>
> 2017-11-30  Qing Zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>
>
>       PR middle_end/79538
>       * gcc.dg/pr79538.c: New test.
>
> ---
> gcc/c-family/c-cppbuiltin.c    | 10 ++++-----
> gcc/fortran/class.c            | 49 ++++++++++++++++++++++++------------------
> gcc/gimple-fold.c              | 13 +++++++++++
> gcc/testsuite/gcc.dg/pr79538.c | 23 ++++++++++++++++++++
> 4 files changed, 69 insertions(+), 26 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/pr79538.c
>
> diff --git a/gcc/c-family/c-cppbuiltin.c b/gcc/c-family/c-cppbuiltin.c
> index 2ac9616..9e33aed 100644
> --- a/gcc/c-family/c-cppbuiltin.c
> +++ b/gcc/c-family/c-cppbuiltin.c
> @@ -1613,7 +1613,7 @@ builtin_define_with_hex_fp_value (const char *macro,
>                                   const char *fp_cast)
> {
>   REAL_VALUE_TYPE real;
> -  char dec_str[64], buf1[256], buf2[256];
> +  char dec_str[64], buf[256], buf1[128], buf2[64];
>
>   /* This is very expensive, so if possible expand them lazily.  */
>   if (lazy_hex_fp_value_count < 12
> @@ -1656,11 +1656,11 @@ builtin_define_with_hex_fp_value (const char *macro,
>
>   /* Assemble the macro in the following fashion
>      macro = fp_cast [dec_str fp_suffix] */
> -  sprintf (buf1, "%s%s", dec_str, fp_suffix);
> -  sprintf (buf2, fp_cast, buf1);
> -  sprintf (buf1, "%s=%s", macro, buf2);
> +  sprintf (buf2, "%s%s", dec_str, fp_suffix);
> +  sprintf (buf1, fp_cast, buf2);
> +  sprintf (buf, "%s=%s", macro, buf1);
>
> -  cpp_define (parse_in, buf1);
> +  cpp_define (parse_in, buf);
> }

This change looks ok.

> /* Return a string constant for the suffix for a value of type TYPE
> diff --git a/gcc/fortran/class.c b/gcc/fortran/class.c
> index ebbd41b..a08fb8d 100644
> --- a/gcc/fortran/class.c
> +++ b/gcc/fortran/class.c
> @@ -602,7 +602,8 @@ bool
> gfc_build_class_symbol (gfc_typespec *ts, symbol_attribute *attr,
>                         gfc_array_spec **as)
> {
> -  char name[GFC_MAX_SYMBOL_LEN+1], tname[GFC_MAX_SYMBOL_LEN+1];
> +  char tname[GFC_MAX_SYMBOL_LEN+1];
> +  char *name;
>   gfc_symbol *fclass;
>   gfc_symbol *vtab;
>   gfc_component *c;
> @@ -633,17 +634,17 @@ gfc_build_class_symbol (gfc_typespec *ts, symbol_attribute *attr,
>   rank = !(*as) || (*as)->rank == -1 ? GFC_MAX_DIMENSIONS : (*as)->rank;
>   get_unique_hashed_string (tname, ts->u.derived);
>   if ((*as) && attr->allocatable)
> -    sprintf (name, "__class_%s_%d_%da", tname, rank, (*as)->corank);
> +    name = xasprintf ("__class_%s_%d_%da", tname, rank, (*as)->corank);
>   else if ((*as) && attr->pointer)
> -    sprintf (name, "__class_%s_%d_%dp", tname, rank, (*as)->corank);
> +    name = xasprintf ("__class_%s_%d_%dp", tname, rank, (*as)->corank);
>   else if ((*as))
> -    sprintf (name, "__class_%s_%d_%dt", tname, rank, (*as)->corank);
> +    name = xasprintf ("__class_%s_%d_%dt", tname, rank, (*as)->corank);
>   else if (attr->pointer)
> -    sprintf (name, "__class_%s_p", tname);
> +    name = xasprintf ("__class_%s_p", tname);
>   else if (attr->allocatable)
> -    sprintf (name, "__class_%s_a", tname);
> +    name = xasprintf ("__class_%s_a", tname);
>   else
> -    sprintf (name, "__class_%s_t", tname);
> +    name = xasprintf ("__class_%s_t", tname);
>
>   if (ts->u.derived->attr.unlimited_polymorphic)
>     {
> @@ -738,6 +739,7 @@ gfc_build_class_symbol (gfc_typespec *ts, symbol_attribute *attr,
>   ts->u.derived = fclass;
>   attr->allocatable = attr->pointer = attr->dimension = attr->codimension = 0;
>   (*as) = NULL;
> +  free (name);
>   return true;
> }
>
> @@ -1527,7 +1529,7 @@ generate_finalization_wrapper (gfc_symbol *derived, gfc_namespace *ns,
>   gfc_component *comp;
>   gfc_namespace *sub_ns;
>   gfc_code *last_code, *block;
> -  char name[GFC_MAX_SYMBOL_LEN+1];
> +  char *name;
>   bool finalizable_comp = false;
>   bool expr_null_wrapper = false;
>   gfc_expr *ancestor_wrapper = NULL, *rank;
> @@ -1606,7 +1608,7 @@ generate_finalization_wrapper (gfc_symbol *derived, gfc_namespace *ns,
>   sub_ns->resolved = 1;
>
>   /* Set up the procedure symbol.  */
> -  sprintf (name, "__final_%s", tname);
> +  name = xasprintf ("__final_%s", tname);
>   gfc_get_symbol (name, sub_ns, &final);
>   sub_ns->proc_name = final;
>   final->attr.flavor = FL_PROCEDURE;
> @@ -2172,6 +2174,7 @@ generate_finalization_wrapper (gfc_symbol *derived, gfc_namespace *ns,
>   gfc_free_expr (rank);
>   vtab_final->initializer = gfc_lval_expr_from_sym (final);
>   vtab_final->ts.interface = final;
> +  free (name);
> }
>
>
> @@ -2239,10 +2242,11 @@ gfc_find_derived_vtab (gfc_symbol *derived)
>
>   if (ns)
>     {
> -      char name[GFC_MAX_SYMBOL_LEN+1], tname[GFC_MAX_SYMBOL_LEN+1];
> +      char tname[GFC_MAX_SYMBOL_LEN+1];
> +      char *name;
>
>       get_unique_hashed_string (tname, derived);
> -      sprintf (name, "__vtab_%s", tname);
> +      name = xasprintf ("__vtab_%s", tname);
>
>       /* Look for the vtab symbol in various namespaces.  */
>       if (gsym && gsym->ns)
> @@ -2270,7 +2274,7 @@ gfc_find_derived_vtab (gfc_symbol *derived)
>           vtab->attr.vtab = 1;
>           vtab->attr.access = ACCESS_PUBLIC;
>           gfc_set_sym_referenced (vtab);
> -         sprintf (name, "__vtype_%s", tname);
> +         name = xasprintf ("__vtype_%s", tname);
>
>           gfc_find_symbol (name, ns, 0, &vtype);
>           if (vtype == NULL)
> @@ -2373,7 +2377,7 @@ gfc_find_derived_vtab (gfc_symbol *derived)
>               else
>                 {
>                   /* Construct default initialization variable.  */
> -                 sprintf (name, "__def_init_%s", tname);
> +                 name = xasprintf ("__def_init_%s", tname);
>                   gfc_get_symbol (name, ns, &def_init);
>                   def_init->attr.target = 1;
>                   def_init->attr.artificial = 1;
> @@ -2406,7 +2410,7 @@ gfc_find_derived_vtab (gfc_symbol *derived)
>                   ns->contained = sub_ns;
>                   sub_ns->resolved = 1;
>                   /* Set up procedure symbol.  */
> -                 sprintf (name, "__copy_%s", tname);
> +                 name = xasprintf ("__copy_%s", tname);
>                   gfc_get_symbol (name, sub_ns, &copy);
>                   sub_ns->proc_name = copy;
>                   copy->attr.flavor = FL_PROCEDURE;
> @@ -2483,7 +2487,7 @@ gfc_find_derived_vtab (gfc_symbol *derived)
>                   ns->contained = sub_ns;
>                   sub_ns->resolved = 1;
>                   /* Set up procedure symbol.  */
> -                 sprintf (name, "__deallocate_%s", tname);
> +                 name = xasprintf ("__deallocate_%s", tname);
>                   gfc_get_symbol (name, sub_ns, &dealloc);
>                   sub_ns->proc_name = dealloc;
>                   dealloc->attr.flavor = FL_PROCEDURE;
> @@ -2532,6 +2536,7 @@ have_vtype:
>           vtab->ts.u.derived = vtype;
>           vtab->value = gfc_default_initializer (&vtab->ts);
>         }
> +      free (name);
>     }
>
>   found_sym = vtab;
> @@ -2623,13 +2628,14 @@ find_intrinsic_vtab (gfc_typespec *ts)
>
>   if (ns)
>     {
> -      char name[GFC_MAX_SYMBOL_LEN+1], tname[GFC_MAX_SYMBOL_LEN+1];
> -
> +      char tname[GFC_MAX_SYMBOL_LEN+1];
> +      char *name;
> +
>       /* Encode all types as TYPENAME_KIND_ including especially character
>          arrays, whose length is now consistently stored in the _len component
>          of the class-variable.  */
>       sprintf (tname, "%s_%d_", gfc_basic_typename (ts->type), ts->kind);
> -      sprintf (name, "__vtab_%s", tname);
> +      name = xasprintf ("__vtab_%s", tname);
>
>       /* Look for the vtab symbol in the top-level namespace only.  */
>       gfc_find_symbol (name, ns, 0, &vtab);
> @@ -2646,7 +2652,7 @@ find_intrinsic_vtab (gfc_typespec *ts)
>           vtab->attr.vtab = 1;
>           vtab->attr.access = ACCESS_PUBLIC;
>           gfc_set_sym_referenced (vtab);
> -         sprintf (name, "__vtype_%s", tname);
> +         name = xasprintf ("__vtype_%s", tname);
>
>           gfc_find_symbol (name, ns, 0, &vtype);
>           if (vtype == NULL)
> @@ -2722,12 +2728,12 @@ find_intrinsic_vtab (gfc_typespec *ts)
>               c->tb->ppc = 1;
>
>               if (ts->type != BT_CHARACTER)
> -               sprintf (name, "__copy_%s", tname);
> +               name = xasprintf ("__copy_%s", tname);
>               else
>                 {
>                   /* __copy is always the same for characters.
>                      Check to see if copy function already exists.  */
> -                 sprintf (name, "__copy_character_%d", ts->kind);
> +                 name = xasprintf ("__copy_character_%d", ts->kind);
>                   contained = ns->contained;
>                   for (; contained; contained = contained->sibling)
>                     if (contained->proc_name
> @@ -2796,6 +2802,7 @@ find_intrinsic_vtab (gfc_typespec *ts)
>           vtab->ts.u.derived = vtype;
>           vtab->value = gfc_default_initializer (&vtab->ts);
>         }
> +      free (name);

It looks like this might be in a performance critical lookup path
where we'd really
like to avoid allocating/freeing memory.  Why's GFC_MAX_SYMBOL_LEN+1 not
enough?  Leaving for fortran folks to comment - note you should CC
fortran@gcc.gnu.org
for fortran patches (done).

>     }
>
>   found_sym = vtab;
> diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
> index 353a46e..fef1969 100644
> --- a/gcc/gimple-fold.c
> +++ b/gcc/gimple-fold.c
> @@ -1323,6 +1323,19 @@ get_range_strlen (tree arg, tree length[2], bitmap *visited, int type,
>                  the array could have zero length.  */
>               *minlen = ssize_int (0);
>             }
> +
> +          if (VAR_P (arg)
> +              && TREE_CODE (TREE_TYPE (arg)) == ARRAY_TYPE)
> +            {
> +              val = TYPE_SIZE_UNIT (TREE_TYPE (arg));
> +              if (!val || integer_zerop (val))

val might be non-constant so you also need to check TREE_CODE (val) !=
INTEGER_CST here.

> +                return false;
> +              val = fold_build2 (MINUS_EXPR, TREE_TYPE (val), val,
> +                                 integer_one_node);

   val = wide_int_to_tree (TREE_TYPE (val), wi::minus (wi::to_wide (val), 1));

you pass a possibly bogus type of 1 to fold_build2 above so the wide-int variant
is prefered.

The gimple-fold.c changes are ok with that change.

Richard.

> +              /* Set the minimum size to zero since the string in
> +                 the array could have zero length.  */
> +              *minlen = ssize_int (0);
> +            }
>         }
>
>       if (!val)
> diff --git a/gcc/testsuite/gcc.dg/pr79538.c b/gcc/testsuite/gcc.dg/pr79538.c
> new file mode 100644
> index 0000000..c5a631e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr79538.c
> @@ -0,0 +1,23 @@
> +/* PR middle-end/79538 - missing -Wformat-overflow with %s and non-member array arguments
> +   { dg-do compile }
> +   { dg-options "-O2 -Wformat-overflow" } */
> +
> +char a3[3];
> +char a4[4];
> +char d[3];
> +
> +void g (int i)
> +{
> +  const char *s = i < 0 ? a3 : a4;
> +  __builtin_sprintf (d, "%s", s);      /* { dg-warning ".__builtin_sprintf. may write a terminating nul past the end of the destination" } */
> +  return;
> +}
> +
> +void f ()
> +{
> +  char des[3];
> +  char src[] = "abcd";
> +  __builtin_sprintf (des, "%s", src); /* { dg-warning "directive writing up to 4 bytes into a region of size 3" } */
> +  return;
> +}
> +
> --
> 1.9.1