Re: [V3][PATCH 2/3] Use the counted_by atribute info in builtin object size [PR108896]

[Qing Zhao <qing.zhao@oracle.com>]

Ping.

thanks.

Qing

> On Aug 25, 2023, at 11:24 AM, Qing Zhao <qing.zhao@oracle.com> wrote:
> 
> Use the counted_by atribute info in builtin object size to compute the
> subobject size for flexible array members.
> 
> gcc/ChangeLog:
> 
> 	PR C/108896
> 	* tree-object-size.cc (addr_object_size): Use the counted_by
> 	attribute info.
> 	* tree.cc (component_ref_has_counted_by_p): New function.
> 	(component_ref_get_counted_by): New function.
> 	* tree.h (component_ref_has_counted_by_p): New prototype.
> 	(component_ref_get_counted_by): New prototype.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR C/108896
> 	* gcc.dg/flex-array-counted-by-2.c: New test.
> 	* gcc.dg/flex-array-counted-by-3.c: New test.
> ---
> .../gcc.dg/flex-array-counted-by-2.c          |  74 ++++++
> .../gcc.dg/flex-array-counted-by-3.c          | 210 ++++++++++++++++++
> gcc/tree-object-size.cc                       |  37 ++-
> gcc/tree.cc                                   |  95 +++++++-
> gcc/tree.h                                    |  10 +
> 5 files changed, 418 insertions(+), 8 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-2.c
> create mode 100644 gcc/testsuite/gcc.dg/flex-array-counted-by-3.c
> 
> diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c
> new file mode 100644
> index 000000000000..ec580c1f1f01
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-2.c
> @@ -0,0 +1,74 @@
> +/* test the attribute counted_by and its usage in
> + * __builtin_dynamic_object_size.  */ 
> +/* { dg-do run } */
> +/* { dg-options "-O2" } */
> +
> +#include "builtin-object-size-common.h"
> +
> +#define expect(p, _v) do { \
> +    size_t v = _v; \
> +    if (p == v) \
> +	__builtin_printf ("ok:  %s == %zd\n", #p, p); \
> +    else \
> +	{  \
> +	  __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> +	  FAIL (); \
> +	} \
> +} while (0);
> +
> +struct flex {
> +  int b;
> +  int c[];
> +} *array_flex;
> +
> +struct annotated {
> +  int b;
> +  int c[] __attribute__ ((counted_by (b)));
> +} *array_annotated;
> +
> +struct nested_annotated {
> +  struct {
> +    union {
> +      int b;
> +      float f;	
> +    };
> +    int n;
> +  };
> +  int c[] __attribute__ ((counted_by (b)));
> +} *array_nested_annotated;
> +
> +void __attribute__((__noinline__)) setup (int normal_count, int attr_count)
> +{
> +  array_flex
> +    = (struct flex *)malloc (sizeof (struct flex)
> +			     + normal_count *  sizeof (int));
> +  array_flex->b = normal_count;
> +
> +  array_annotated
> +    = (struct annotated *)malloc (sizeof (struct annotated)
> +				  + attr_count *  sizeof (int));
> +  array_annotated->b = attr_count;
> +
> +  array_nested_annotated
> +    = (struct nested_annotated *)malloc (sizeof (struct nested_annotated)
> +					 + attr_count *  sizeof (int));
> +  array_nested_annotated->b = attr_count;
> +
> +  return;
> +}
> +
> +void __attribute__((__noinline__)) test ()
> +{
> +    expect(__builtin_dynamic_object_size(array_flex->c, 1), -1);
> +    expect(__builtin_dynamic_object_size(array_annotated->c, 1),
> +	   array_annotated->b * sizeof (int));
> +    expect(__builtin_dynamic_object_size(array_nested_annotated->c, 1),
> +	   array_nested_annotated->b * sizeof (int));
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +  setup (10,10);   
> +  test ();
> +  DONE ();
> +}
> diff --git a/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c
> new file mode 100644
> index 000000000000..a0c3cb88ec71
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/flex-array-counted-by-3.c
> @@ -0,0 +1,210 @@
> +/* test the attribute counted_by and its usage in
> +__builtin_dynamic_object_size: what's the correct behavior when the
> +allocation size mismatched with the value of counted_by attribute?  */
> +/* { dg-do run } */
> +/* { dg-options "-O -fstrict-flex-arrays=3" } */
> +
> +#include "builtin-object-size-common.h"
> +
> +struct annotated {
> +  size_t foo;
> +  char others;
> +  char array[] __attribute__((counted_by (foo)));
> +};
> +
> +#define expect(p, _v) do { \
> +    size_t v = _v; \
> +    if (p == v) \
> +        __builtin_printf ("ok:  %s == %zd\n", #p, p); \
> +    else \
> +        {  \
> +          __builtin_printf ("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> +	  FAIL (); \
> +        } \
> +} while (0);
> +
> +#define noinline __attribute__((__noinline__))
> +#define SIZE_BUMP 10 
> +#define MAX(a, b) ((a) > (b) ? (a) : (b))
> +#define MIN(a, b) ((a) < (b) ? (a) : (b))
> +
> +/* In general, Due to type casting, the type for the pointee of a pointer
> +   does not say anything about the object it points to,
> +   So, __builtin_object_size can not directly use the type of the pointee
> +   to decide the size of the object the pointer points to.
> +
> +   there are only two reliable ways:
> +   A. observed allocations  (call to the allocation functions in the routine)
> +   B. observed accesses     (read or write access to the location of the
> +                             pointer points to)
> +
> +   that provide information about the type/existence of an object at
> +   the corresponding address.
> +
> +   for A, we use the "alloc_size" attribute for the corresponding allocation
> +   functions to determine the object size;
> +
> +   For B, we use the SIZE info of the TYPE attached to the corresponding access.
> +   (We treat counted_by attribute as a complement to the SIZE info of the TYPE
> +    for FMA)
> +
> +   The only other way in C which ensures that a pointer actually points
> +   to an object of the correct type is 'static':
> +
> +   void foo(struct P *p[static 1]);
> +
> +   See https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624814.html
> +   for more details.  */
> +
> +/* in the following function, malloc allocated more space than the value
> +   of counted_by attribute.  Then what's the correct behavior we expect
> +   the __builtin_dynamic_object_size should have for each of the cases?  */
> +
> +static struct annotated * noinline alloc_buf_more (size_t index)
> +{
> +  struct annotated *p;
> +  size_t allocated_size
> +    = MAX (sizeof (struct annotated),
> +	   (__builtin_offsetof (struct annotated, array[0])
> +	    + (index + SIZE_BUMP) * sizeof (char)));
> +  p = (struct annotated *) malloc (allocated_size);
> +
> +  p->foo = index;
> +
> +  /*when checking the observed access p->array, we have info on both
> +    observered allocation and observed access,
> +    A. from observed allocation: 
> +    	allocated_size - offsetof (struct annotated, array[0])
> +    B. from observed access: p->foo * sizeof (char)
> +   */
> +
> +  /* for size in the whole object: always uses A.  */
> +  /* for size in the sub-object: chose the smaller of A and B.
> +   * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html
> +   * for details on why.  */
> +
> +  /* for MAXIMUM size in the whole object: use the allocation size
> +     for the whole object.  */
> +  expect(__builtin_dynamic_object_size(p->array, 0),
> +	 allocated_size - __builtin_offsetof (struct annotated, array[0]));
> +
> +  /* for MAXIMUM size in the sub-object. use the smaller of A and B.  */
> +  expect(__builtin_dynamic_object_size(p->array, 1),
> +	 MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]),
> +	      (p->foo) * sizeof(char)));
> +
> +  /* for MINIMUM size in the whole object: use the allocation size
> +     for the whole object.  */
> +  expect(__builtin_dynamic_object_size(p->array, 2),
> +	 allocated_size - __builtin_offsetof (struct annotated, array[0]));
> +
> +  /* for MINIMUM size in the sub-object: use the smaller of A and B.  */
> +  expect(__builtin_dynamic_object_size(p->array, 3),
> +	 MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]),
> +	      (p->foo) * sizeof(char)));
> +
> +  /*when checking the pointer p, we only have info on the observed allocation.
> +    So, the object size info can only been obtained from the call to malloc.
> +    for both MAXIMUM and MINIMUM: A = (index + SIZE_BUMP) * sizeof (char)  */
> +  expect(__builtin_dynamic_object_size(p, 0), allocated_size);
> +  expect(__builtin_dynamic_object_size(p, 1), allocated_size);
> +  expect(__builtin_dynamic_object_size(p, 2), allocated_size);
> +  expect(__builtin_dynamic_object_size(p, 3), allocated_size);
> +  return p;
> +}
> +
> +/* in the following function, malloc allocated less space than the value
> +   of counted_by attribute.  Then what's the correct behavior we expect
> +   the __builtin_dynamic_object_size should have for each of the cases?
> +   NOTE: this is an user error, GCC should issue warnings for such case.
> +   this is a seperate issue we should address later.  */
> +
> +static struct annotated * noinline alloc_buf_less (size_t index)
> +{
> +  struct annotated *p;
> +  size_t allocated_size
> +    = MAX (sizeof (struct annotated),
> +	   (__builtin_offsetof (struct annotated, array[0])
> +	    + (index) * sizeof (char)));
> +  p = (struct annotated *) malloc (allocated_size);
> +
> +  p->foo = index + SIZE_BUMP;
> +
> +  /*when checking the observed access p->array, we have info on both
> +    observered allocation and observed access,
> +    A. from observed allocation:
> +    	allocated_size - offsetof (struct annotated, array[0])
> +    B. from observed access: p->foo * sizeof (char)
> +   */
> +
> +  /* for size in the whole object: always uses A.  */
> +  /* for size in the sub-object: chose the smaller of A and B.
> +   * Please see https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625891.html
> +   * for details on why.  */
> +
> +  /* for MAXIMUM size in the whole object: use the allocation size
> +     for the whole object.  */
> +  expect(__builtin_dynamic_object_size(p->array, 0),
> +	 allocated_size - __builtin_offsetof (struct annotated, array[0]));
> +
> +  /* for MAXIMUM size in the sub-object. use the smaller of A and B.  */
> +  expect(__builtin_dynamic_object_size(p->array, 1),
> +	 MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]),
> +	      (p->foo) * sizeof(char)));
> +
> +  /* for MINIMUM size in the whole object: use the allocation size
> +     for the whole object.  */
> +  expect(__builtin_dynamic_object_size(p->array, 2),
> +	 allocated_size - __builtin_offsetof (struct annotated, array[0]));
> +
> +  /* for MINIMUM size in the sub-object: use the smaller of A and B.  */
> +  expect(__builtin_dynamic_object_size(p->array, 3),
> +	 MIN (allocated_size - __builtin_offsetof (struct annotated, array[0]),
> +	      (p->foo) * sizeof(char)));
> +
> +  /*when checking the pointer p, we only have info on the observed
> +    allocation. So, the object size info can only been obtained from
> +    the call to malloc.  */
> +  expect(__builtin_dynamic_object_size(p, 0), allocated_size);
> +  expect(__builtin_dynamic_object_size(p, 1), allocated_size);
> +  expect(__builtin_dynamic_object_size(p, 2), allocated_size);
> +  expect(__builtin_dynamic_object_size(p, 3), allocated_size);
> +  return p;
> +}
> +
> +int main ()
> +{
> +  struct annotated *p, *q;
> +  p = alloc_buf_more (10);
> +  q = alloc_buf_less (10);
> +
> +  /*when checking the observed access p->array, we only have info on the
> +    observed access, i.e, the TYPE_SIZE info from the access. We don't have
> +    info on the whole object.  */
> +  expect(__builtin_dynamic_object_size(p->array, 0), -1);
> +  expect(__builtin_dynamic_object_size(p->array, 1), p->foo * sizeof(char));
> +  expect(__builtin_dynamic_object_size(p->array, 2), 0);
> +  expect(__builtin_dynamic_object_size(p->array, 3), p->foo * sizeof(char));
> +  /*when checking the pointer p, we have no observed allocation nor observed
> +    access, therefore, we cannot determine the size info here.  */
> +  expect(__builtin_dynamic_object_size(p, 0), -1);
> +  expect(__builtin_dynamic_object_size(p, 1), -1);
> +  expect(__builtin_dynamic_object_size(p, 2), 0);
> +  expect(__builtin_dynamic_object_size(p, 3), 0);
> +
> +  /*when checking the observed access p->array, we only have info on the
> +    observed access, i.e, the TYPE_SIZE info from the access. We don't have
> +    info on the whole object.  */
> +  expect(__builtin_dynamic_object_size(q->array, 0), -1);
> +  expect(__builtin_dynamic_object_size(q->array, 1), q->foo * sizeof(char));
> +  expect(__builtin_dynamic_object_size(q->array, 2), 0);
> +  expect(__builtin_dynamic_object_size(q->array, 3), q->foo * sizeof(char));
> +  /*when checking the pointer p, we have no observed allocation nor observed
> +    access, therefore, we cannot determine the size info here.  */
> +  expect(__builtin_dynamic_object_size(q, 0), -1);
> +  expect(__builtin_dynamic_object_size(q, 1), -1);
> +  expect(__builtin_dynamic_object_size(q, 2), 0);
> +  expect(__builtin_dynamic_object_size(q, 3), 0);
> +
> +  DONE ();
> +}
> diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc
> index a62af0500563..cf7843c5684b 100644
> --- a/gcc/tree-object-size.cc
> +++ b/gcc/tree-object-size.cc
> @@ -585,6 +585,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr,
>   if (pt_var != TREE_OPERAND (ptr, 0))
>     {
>       tree var;
> +      tree counted_by_ref = NULL_TREE;
> 
>       if (object_size_type & OST_SUBOBJECT)
> 	{
> @@ -600,11 +601,12 @@ addr_object_size (struct object_size_info *osi, const_tree ptr,
> 	    var = TREE_OPERAND (var, 0);
> 	  if (var != pt_var && TREE_CODE (var) == ARRAY_REF)
> 	    var = TREE_OPERAND (var, 0);
> -	  if (! TYPE_SIZE_UNIT (TREE_TYPE (var))
> +	  if (! component_ref_has_counted_by_p (var)
> +	     && ((! TYPE_SIZE_UNIT (TREE_TYPE (var))
> 	      || ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var)))
> 	      || (pt_var_size && TREE_CODE (pt_var_size) == INTEGER_CST
> 		  && tree_int_cst_lt (pt_var_size,
> -				      TYPE_SIZE_UNIT (TREE_TYPE (var)))))
> +				      TYPE_SIZE_UNIT (TREE_TYPE (var)))))))
> 	    var = pt_var;
> 	  else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF)
> 	    {
> @@ -612,6 +614,7 @@ addr_object_size (struct object_size_info *osi, const_tree ptr,
> 	      /* For &X->fld, compute object size if fld isn't a flexible array
> 		 member.  */
> 	      bool is_flexible_array_mem_ref = false;
> +
> 	      while (v && v != pt_var)
> 		switch (TREE_CODE (v))
> 		  {
> @@ -660,6 +663,8 @@ addr_object_size (struct object_size_info *osi, const_tree ptr,
> 		    /* Now the ref is to an array type.  */
> 		    gcc_assert (TREE_CODE (TREE_TYPE (v)) == ARRAY_TYPE);
> 		    is_flexible_array_mem_ref = array_ref_flexible_size_p (v);
> +		    counted_by_ref = component_ref_get_counted_by (v);
> +
> 		    while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
> 		      if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
> 			  != UNION_TYPE
> @@ -673,8 +678,11 @@ addr_object_size (struct object_size_info *osi, const_tree ptr,
> 			   == RECORD_TYPE)
> 		      {
> 			/* compute object size only if v is not a
> -			   flexible array member.  */
> -			if (!is_flexible_array_mem_ref)
> +			   flexible array member or the flexible array member
> +			   has a known element count indicated by the user
> +			   through attribute counted_by.  */
> +			if (!is_flexible_array_mem_ref
> +			    || counted_by_ref)
> 			  {
> 			    v = NULL_TREE;
> 			    break;
> @@ -707,9 +715,24 @@ addr_object_size (struct object_size_info *osi, const_tree ptr,
> 
>       if (var != pt_var)
> 	{
> -	  var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
> -	  if (!TREE_CONSTANT (var_size))
> -	    var_size = get_or_create_ssa_default_def (cfun, var_size);
> +	  if (!counted_by_ref)
> +	    {
> +	      var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
> +	      if (!TREE_CONSTANT (var_size))
> +		var_size = get_or_create_ssa_default_def (cfun, var_size);
> +	    }
> +	  else
> +	    {
> +	      gcc_assert (TREE_CODE (var) == COMPONENT_REF
> +			  && TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE);
> +	      tree element_size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (var)));
> +	      var_size
> +		= size_binop (MULT_EXPR,
> +			      fold_convert (sizetype, counted_by_ref),
> +			      fold_convert (sizetype, element_size));
> +	      if (!todo)
> +		todo = TODO_update_ssa_only_virtuals;
> +	    }
> 	  if (!var_size)
> 	    return false;
> 	}
> diff --git a/gcc/tree.cc b/gcc/tree.cc
> index fcd36ae0cd74..3b6ddcbdcbf8 100644
> --- a/gcc/tree.cc
> +++ b/gcc/tree.cc
> @@ -12745,6 +12745,32 @@ array_ref_element_size (tree exp)
>     return SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (elmt_type), exp);
> }
> 
> +/*  For a component_ref that has an array type ARRAY_REF, return TRUE when
> +    an counted_by attribute attached to the corresponding FIELD_DECL.
> +    return FALSE otherwise.  */
> +bool
> +component_ref_has_counted_by_p (tree array_ref)
> +{
> +  if (TREE_CODE (array_ref) != COMPONENT_REF)
> +    return false;
> +
> +  if (TREE_CODE (TREE_TYPE (array_ref)) != ARRAY_TYPE)
> +    return false;
> +
> +  tree struct_object = TREE_OPERAND (array_ref, 0);
> +  tree struct_type = TREE_TYPE (struct_object);
> +
> +  if (!RECORD_OR_UNION_TYPE_P (struct_type))
> +    return false;
> +  tree field_decl = TREE_OPERAND (array_ref, 1);
> +  tree attr_counted_by = lookup_attribute ("counted_by",
> +					      DECL_ATTRIBUTES (field_decl));
> +
> +  if (!attr_counted_by)
> +    return false;
> +  return true;
> +}
> +
> /* Given a field list, FIELDLIST, of a structure/union, return a TREE_LIST,
>    with each TREE_VALUE a FIELD_DECL stepping down the chain to the FIELD
>    whose name is FIELDNAME, which is the last TREE_VALUE of the list.
> @@ -12771,7 +12797,7 @@ get_named_field (tree fieldlist, const char *fieldname)
> 	 fields inside it recursively.  */
>       else if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (field)))
> 	  if ((named_field = get_named_field (TYPE_FIELDS (TREE_TYPE (field)),
> -						  fieldname)) != NULL_TREE)
> +					     fieldname)) != NULL_TREE)
> 	    {
> 	      named_field = tree_cons (NULL_TREE, field, named_field);
> 	      break;
> @@ -12784,6 +12810,73 @@ get_named_field (tree fieldlist, const char *fieldname)
>   return named_field;
> }
> 
> +/* For a component_ref that has an array type ARRAY_REF, get the object that
> +   represents its counted_by per the attribute counted_by attached to
> +   the corresponding FIELD_DECL.  return NULL_TREE when cannot find such
> +   object.
> +   For example, if:
> +
> +    struct P {
> +      int k;
> +      int x[] __attribute__ ((counted_by (k)));
> +    } *p;
> +
> +    for the following reference:
> +
> +    p->x[b]
> +
> +    the object that represents its element count will be:
> +
> +    p->k
> +
> +    So, when component_ref_get_counted_by (p->x[b]) is called, p->k should be
> +    returned.
> +*/
> +
> +tree
> +component_ref_get_counted_by (tree array_ref)
> +{
> +  if (! component_ref_has_counted_by_p (array_ref))
> +    return NULL_TREE;
> +
> +  tree struct_object = TREE_OPERAND (array_ref, 0);
> +  tree struct_type = TREE_TYPE (struct_object);
> +  tree field_decl = TREE_OPERAND (array_ref, 1);
> +  tree attr_counted_by = lookup_attribute ("counted_by",
> +					   DECL_ATTRIBUTES (field_decl));
> +  gcc_assert (attr_counted_by);
> +
> +  /* If there is an counted_by attribute attached to the field,
> +     get the field that maps to the counted_by.  */
> +
> +  const char *fieldname
> +    = IDENTIFIER_POINTER (TREE_VALUE (TREE_VALUE (attr_counted_by)));
> +
> +  tree counted_by_field = get_named_field (TYPE_FIELDS (struct_type),
> +					   fieldname);
> +
> +  gcc_assert (counted_by_field);
> +
> +  /* generate the tree node that represent the counted_by of this array
> +     ref.  This is a (possible nested) COMPONENT_REF to the counted_by_field
> +     of the containing structure.  */
> +
> +  tree counted_by_ref = NULL_TREE;
> +  tree object = struct_object;
> +  do
> +    {
> +      tree field = TREE_VALUE (counted_by_field);
> +
> +      counted_by_ref = build3 (COMPONENT_REF,
> +			       TREE_TYPE (field),
> +			       unshare_expr (object), field,
> +			       NULL_TREE);
> +      object = counted_by_ref;
> +      counted_by_field = TREE_CHAIN (counted_by_field);
> +    }
> +  while (counted_by_field);
> +  return counted_by_ref;
> +}
> 
> /* Return a tree representing the lower bound of the array mentioned in
>    EXP, an ARRAY_REF or an ARRAY_RANGE_REF.  */
> diff --git a/gcc/tree.h b/gcc/tree.h
> index 4859becaa1e7..07eed7219835 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -5619,11 +5619,21 @@ extern tree get_base_address (tree t);
>    of EXP, an ARRAY_REF or an ARRAY_RANGE_REF.  */
> extern tree array_ref_element_size (tree);
> 
> +/* Give a component_ref that has an array type, return true when an
> +   attribute counted_by attached to the corresponding FIELD_DECL.  */
> +extern bool component_ref_has_counted_by_p (tree);
> +
> /* Given a field list, FIELDLIST, of a structure/union, return the FIELD whose
>    name is FIELDNAME, return NULL_TREE if such field is not found.
>    searching nested anonymous structure/union recursively.  */
> extern tree get_named_field (tree, const char *);
> 
> +/* Give a component_ref that has an array type, return the object that
> +   represents its counted_by per the attribute counted_by attached to
> +   the corresponding FIELD_DECL.  return NULL_TREE when cannot find such
> +   object.  */
> +extern tree component_ref_get_counted_by (tree);
> +
> /* Return a typenode for the "standard" C type with a given name.  */
> extern tree get_typenode_from_name (const char *);
> 
> -- 
> 2.31.1
>