On Thu, Aug 21, 2025 at 12:59 AM Andrew Pinski
<andrew.pin...@oss.qualcomm.com> wrote:
>
> On Thu, Aug 21, 2025 at 12:41 AM Kees Cook <k...@kernel.org> wrote:
>>
>> To support the KCFI type-id which needs to convert unique function
>> prototypes into unique 32-bit values, add a subset of the Itanium C++
>> mangling ABI for C typeinfo of function prototypes. This gets us to the
>> first step: a string representation of the function prototype.
>
>
> Can you explain why this is needed? Also it seems like the code is very
> sensitive to buffer overflows. Especially the way it is currently written.
> The C++ front-end version uses obstack_grow to overcome the buffer overflow
> issue.
So looking at where this is only used; You should calculate the hash
directly instead.
So basically places where you do *(p++) = 'x'; replace it with doing
the hash calculation.
Add a few functions like:
hash add_hash (hash, char);
hash add_hash (hash, char*);
hash add_hash_int (hash, int);
Etc.
Thanks,
Andrew
>
>>
>>
>> Trying to extract only the C portions of the gcc/cp/mangle.cc code
>> seemed infeasible after a few attempts. So this is the minimal subset
>> of the mangling ABI needed to generate unique KCFI type ids.
>>
>> I could not find a way to build a sensible selftest infrastructure for
>> this code. I wanted to do something like this:
>>
>> #ifdef CHECKING_P
>> const char code[] = "
>> typedef struct { int x, y } xy_t;
>> extern int func(xy_t *p);
>> ";
>>
>> ASSERT_MANGLE (code, "_ZTSPFiP4xy_tE");
>> ...
>> #endif
>>
>> But I could not find any way to build a localized parser that could
>> parse the "code" string from which I could extract the "func" fndecl.
>> It would have been so much nicer to build the selftest directly into
>> mangle.cc here, but I couldn't figure it out. Instead, later patches
>> create a "kcfi" dump file, and the large kcfi testsuite validates
>> expected mangle strings as part of the type-id validation.
>>
>> Signed-off-by: Kees Cook <k...@kernel.org>
>> ---
>> gcc/Makefile.in | 1 +
>> gcc/mangle.h | 29 +++
>> gcc/selftest.h | 1 +
>> gcc/mangle.cc | 548 ++++++++++++++++++++++++++++++++++++++++++++++++
>> 4 files changed, 579 insertions(+)
>> create mode 100644 gcc/mangle.h
>> create mode 100644 gcc/mangle.cc
>>
>> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
>> index d7d5cbe72770..86f62611c1d4 100644
>> --- a/gcc/Makefile.in
>> +++ b/gcc/Makefile.in
>> @@ -1619,6 +1619,7 @@ OBJS = \
>> lto-section-out.o \
>> lto-opts.o \
>> lto-compress.o \
>> + mangle.o \
>> mcf.o \
>> mode-switching.o \
>> modulo-sched.o \
>> diff --git a/gcc/mangle.h b/gcc/mangle.h
>> new file mode 100644
>> index 000000000000..94521e1e7e5c
>> --- /dev/null
>> +++ b/gcc/mangle.h
>> @@ -0,0 +1,29 @@
>> +/* Itanium C++ ABI type mangling for GCC.
>> + Copyright (C) 2025 Free Software Foundation, Inc.
>> +
>> +This file is part of GCC.
>> +
>> +GCC is free software; you can redistribute it and/or modify it under
>> +the terms of the GNU General Public License as published by the Free
>> +Software Foundation; either version 3, or (at your option) any later
>> +version.
>> +
>> +GCC is distributed in the hope that it will be useful, but WITHOUT ANY
>> +WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
>> +for more details.
>> +
>> +You should have received a copy of the GNU General Public License
>> +along with GCC; see the file COPYING3. If not see
>> +<http://www.gnu.org/licenses/>. */
>> +
>> +#ifndef GCC_MANGLE_H
>> +#define GCC_MANGLE_H
>> +
>> +#include "tree.h"
>> +
>> +/* Function type mangling following Itanium C++ ABI conventions.
>> + Returns a static buffer containing the mangled type string. */
>> +extern const char *mangle_function_type (tree fntype_or_fndecl);
>> +
>> +#endif /* GCC_MANGLE_H */
>> diff --git a/gcc/mangle.cc b/gcc/mangle.cc
>> new file mode 100644
>> index 000000000000..830985251c81
>> --- /dev/null
>> +++ b/gcc/mangle.cc
>> @@ -0,0 +1,548 @@
>> +/* Itanium C++ ABI type mangling for GCC.
>> + Copyright (C) 2025 Free Software Foundation, Inc.
>> +
>> +This file is part of GCC.
>> +
>> +GCC is free software; you can redistribute it and/or modify it under
>> +the terms of the GNU General Public License as published by the Free
>> +Software Foundation; either version 3, or (at your option) any later
>> +version.
>> +
>> +GCC is distributed in the hope that it will be useful, but WITHOUT ANY
>> +WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
>> +for more details.
>> +
>> +You should have received a copy of the GNU General Public License
>> +along with GCC; see the file COPYING3. If not see
>> +<http://www.gnu.org/licenses/>. */
>> +
>> +#include "config.h"
>> +#include "system.h"
>> +#include "coretypes.h"
>> +#include "tree.h"
>> +#include "diagnostic-core.h"
>> +#include "stringpool.h"
>> +#include "stor-layout.h"
>> +#include "mangle.h"
>> +#include "selftest.h"
>> +
>> +/* Forward declaration for recursive type mangling. */
>> +static void mangle_type_to_buffer (tree type, char **p, char *end);
>> +
>> +/* Mangle a builtin type following Itanium C++ ABI for C types. */
>> +static void
>> +mangle_builtin_type_to_buffer (tree type, char **p, char *end)
>> +{
>> + gcc_assert (type != NULL_TREE);
>> + gcc_assert (p != NULL && *p != NULL && end != NULL);
>> + gcc_assert (*p < end);
>> +
>> + if (*p >= end)
>> + return;
>> +
>> + switch (TREE_CODE (type))
>> + {
>> + case VOID_TYPE:
>> + **p = 'v';
>> + (*p)++;
>> + break;
>> +
>> + case BOOLEAN_TYPE:
>> + **p = 'b';
>> + (*p)++;
>
>
> I am not 100% sure this is always correct. because there could be a boolean
> type with a precision non 1.
>
>>
>> + break;
>> +
>> + case INTEGER_TYPE:
>> + /* Handle standard integer types using Itanium ABI codes. */
>> + if (type == char_type_node)
>> + {
>> + **p = 'c';
>> + (*p)++;
>> + }
>> + else if (type == signed_char_type_node)
>> + {
>> + **p = 'a';
>> + (*p)++;
>> + }
>> + else if (type == unsigned_char_type_node)
>> + {
>> + **p = 'h';
>> + (*p)++;
>> + }
>> + else if (type == short_integer_type_node)
>> + {
>> + **p = 's';
>> + (*p)++;
>> + }
>> + else if (type == short_unsigned_type_node)
>> + {
>> + **p = 't';
>> + (*p)++;
>> + }
>> + else if (type == integer_type_node)
>> + {
>> + **p = 'i';
>> + (*p)++;
>> + }
>> + else if (type == unsigned_type_node)
>> + {
>> + **p = 'j';
>> + (*p)++;
>> + }
>> + else if (type == long_integer_type_node)
>> + {
>> + **p = 'l';
>> + (*p)++;
>> + }
>> + else if (type == long_unsigned_type_node)
>> + {
>> + **p = 'm';
>> + (*p)++;
>> + }
>> + else if (type == long_long_integer_type_node)
>> + {
>> + **p = 'x';
>> + (*p)++;
>> + }
>> + else if (type == long_long_unsigned_type_node)
>> + {
>> + **p = 'y';
>> + (*p)++;
>> + }
>> + else
>> + {
>> + /* Fallback for other integer types - use precision-based
>> encoding. */
>> + *p += snprintf (*p, end - *p, "i%d", TYPE_PRECISION (type));
>> + }
>> + break;
>> +
>> + case REAL_TYPE:
>> + if (type == float_type_node)
>> + {
>> + **p = 'f';
>> + (*p)++;
>> + }
>> + else if (type == double_type_node)
>> + {
>> + **p = 'd';
>> + (*p)++;
>> + }
>> + else if (type == long_double_type_node)
>> + {
>> + **p = 'e';
>> + (*p)++;
>> + }
>> + else
>> + {
>> + /* Fallback for other real types. */
>> + *p += snprintf (*p, end - *p, "f%d", TYPE_PRECISION (type));
>> + }
>> + break;
>
>
> You definitely miss NULLPTR_TYPE.
>
>>
>> +
>> + default:
>> + /* Unknown builtin type - this should never happen in a well-formed C
>> program. */
>> + error ("mangle: Unknown builtin type with %<TREE_CODE%> %d",
>> TREE_CODE (type));
>> + error ("mangle: %<TYPE_MODE%> = %d, %<TYPE_PRECISION%> = %d",
>> TYPE_MODE (type), TYPE_PRECISION (type));
>> + error ("mangle: Please report this as a bug with the above diagnostic
>> information");
>> + gcc_unreachable ();
>
>
> This is wrong way of doing this.
> It should be a sorry or a fatal_error instead. Maybe with an inform
> beforehand.
> You might also want to use get_tree_code_name, GET_MODE_NAME instead of
> printing out a number because the number tells nothing.
> Maybe even use print_tree or print_generic_expr to print out the tree instead
> of manually printing it.
>
>>
>> + }
>> +}
>> +
>> +/* Canonicalize typedef types to their underlying named struct/union types.
>> */
>> +static tree
>> +canonicalize_typedef_type (tree type)
>> +{
>> + /* Handle typedef types - canonicalize to named structs when possible. */
>> + if (TYPE_NAME (type) && TREE_CODE (TYPE_NAME (type)) == TYPE_DECL)
>> + {
>> + tree type_decl = TYPE_NAME (type);
>> +
>> + /* Check if this is a typedef (not the original struct declaration) */
>> + if (DECL_ORIGINAL_TYPE (type_decl))
>> + {
>> + tree original_type = DECL_ORIGINAL_TYPE (type_decl);
>> +
>> + /* If the original type is a named struct/union/enum, use that
>> instead. */
>> + if ((TREE_CODE (original_type) == RECORD_TYPE
>> + || TREE_CODE (original_type) == UNION_TYPE
>> + || TREE_CODE (original_type) == ENUMERAL_TYPE)
>> + && TYPE_NAME (original_type)
>> + && ((TREE_CODE (TYPE_NAME (original_type)) == TYPE_DECL
>> + && DECL_NAME (TYPE_NAME (original_type)))
>> + || TREE_CODE (TYPE_NAME (original_type)) ==
>> IDENTIFIER_NODE))
>> + {
>> + /* Recursively canonicalize in case the original type is also
>> a typedef. */
>> + return canonicalize_typedef_type (original_type);
>> + }
>> +
>> + /* For basic type typedefs (e.g., u8 -> unsigned char),
>> canonicalize to original type. */
>> + if (TREE_CODE (original_type) == INTEGER_TYPE
>> + || TREE_CODE (original_type) == REAL_TYPE
>> + || TREE_CODE (original_type) == POINTER_TYPE
>> + || TREE_CODE (original_type) == ARRAY_TYPE
>> + || TREE_CODE (original_type) == FUNCTION_TYPE
>> + || TREE_CODE (original_type) == METHOD_TYPE
>> + || TREE_CODE (original_type) == BOOLEAN_TYPE
>> + || TREE_CODE (original_type) == COMPLEX_TYPE
>> + || TREE_CODE (original_type) == VECTOR_TYPE)
>> + {
>> + /* Recursively canonicalize in case the original type is also
>> a typedef. */
>> + return canonicalize_typedef_type (original_type);
>> + }
>> + }
>> + }
>> +
>> + return type;
>> +}
>> +
>> +/* Recursively mangle a type following Itanium C++ ABI conventions. */
>> +static void
>> +mangle_type_to_buffer (tree type, char **p, char *end)
>> +{
>> + gcc_assert (type != NULL_TREE);
>> + gcc_assert (p != NULL && *p != NULL && end != NULL);
>> + gcc_assert (*p < end);
>> +
>> + if (*p >= end)
>> + return;
>> +
>> + /* Canonicalize typedef types to their underlying named struct types. */
>> + type = canonicalize_typedef_type (type);
>> +
>> + switch (TREE_CODE (type))
>> + {
>> + case POINTER_TYPE:
>> + {
>> + /* Pointer type: 'P' + qualifiers + pointed-to type. */
>> + **p = 'P';
>> + (*p)++;
>> +
>> + /* Add qualifiers to the pointed-to type following Itanium C++ ABI
>> ordering. */
>> + tree pointed_to_type = TREE_TYPE (type);
>> + if (TYPE_QUALS (pointed_to_type) != TYPE_UNQUALIFIED)
>> + {
>> + /* Emit qualifiers in Itanium ABI order: restrict, volatile,
>> const. */
>> + if (TYPE_QUALS (pointed_to_type) & TYPE_QUAL_RESTRICT)
>> + {
>> + **p = 'r';
>> + (*p)++;
>> + }
>> + if (TYPE_QUALS (pointed_to_type) & TYPE_QUAL_VOLATILE)
>> + {
>> + **p = 'V';
>> + (*p)++;
>> + }
>> + if (TYPE_QUALS (pointed_to_type) & TYPE_QUAL_CONST)
>> + {
>> + **p = 'K';
>> + (*p)++;
>> + }
>> + /* Note: _Atomic is not typically used in kernel code. */
>> + }
>> +
>> + /* For KCFI's hybrid type system: preserve typedef names for
>> compound types,
>> + but use canonical forms for primitive types. */
>> + tree target_type;
>> + if (TREE_CODE (pointed_to_type) == RECORD_TYPE
>> + || TREE_CODE (pointed_to_type) == UNION_TYPE
>> + || TREE_CODE (pointed_to_type) == ENUMERAL_TYPE)
>> + {
>> + /* Compound type: preserve typedef information by using original
>> type. */
>> + target_type = pointed_to_type;
>> + }
>> + else
>> + {
>> + /* Primitive type: use canonical form to ensure structural
>> typing. */
>> + target_type = TYPE_MAIN_VARIANT (pointed_to_type);
>> + }
>> + mangle_type_to_buffer (target_type, p, end);
>> + break;
>> + }
>> +
>> + case ARRAY_TYPE:
>> + /* Array type: 'A' + size + '_' + element type (simplified). */
>> + **p = 'A';
>> + (*p)++;
>> + if (TYPE_DOMAIN (type) && TYPE_MAX_VALUE (TYPE_DOMAIN (type)))
>> + {
>> + HOST_WIDE_INT size = tree_to_shwi (TYPE_MAX_VALUE (TYPE_DOMAIN
>> (type))) + 1;
>
>
> No check to make sure array type is not a VLA. So this will ICE.
>
>>
>> + *p += snprintf (*p, end - *p, "%ld_", (long) size);
>> + }
>> + else
>> + {
>> + **p = '_';
>> + (*p)++;
>> + }
>> + mangle_type_to_buffer (TREE_TYPE (type), p, end);
>> + break;
>> +
>> + case FUNCTION_TYPE:
>> + {
>> + /* Function type: 'F' + return type + parameter types + 'E' */
>> + **p = 'F';
>> + (*p)++;
>> + mangle_type_to_buffer (TREE_TYPE (type), p, end);
>> +
>> + /* Add parameter types. */
>> + tree param_types = TYPE_ARG_TYPES (type);
>> +
>> + if (param_types == NULL_TREE)
>> + {
>> + /* func() - variadic function, no parameter list.
>> + Don't mangle any parameters. */
>> + }
>> + else
>> + {
>> + bool found_real_params = false;
>> + for (tree param = param_types; param && *p < end; param =
>> TREE_CHAIN (param))
>> + {
>> + tree param_type = TREE_VALUE (param);
>> + if (param_type == void_type_node)
>> + {
>> + /* Check if this is the first parameter (explicit void)
>> or a sentinel */
>> + if (!found_real_params)
>> + {
>> + /* func(void) - explicit empty parameter list.
>> + Mangle void to distinguish from variadic func().
>> */
>> + mangle_type_to_buffer (void_type_node, p, end);
>> + }
>> + /* If we found real params before this void, it's a
>> sentinel - stop */
>> + break;
>> + }
>> +
>> + found_real_params = true;
>> +
>> + /* For value parameters, ignore const/volatile qualifiers as
>> they
>> + don't affect the calling convention. const int and int
>> are
>> + passed identically by value. */
>> + tree canonical_param_type = param_type;
>> + if (TREE_CODE (param_type) != POINTER_TYPE
>> + && TREE_CODE (param_type) != REFERENCE_TYPE
>> + && TREE_CODE (param_type) != ARRAY_TYPE)
>> + {
>> + /* Strip qualifiers for non-pointer/reference value
>> parameters. */
>> + canonical_param_type = TYPE_MAIN_VARIANT (param_type);
>> + }
>> +
>> + mangle_type_to_buffer (canonical_param_type, p, end);
>> + }
>> + }
>> +
>> + **p = 'E';
>> + (*p)++;
>> + break;
>> + }
>> +
>> + case RECORD_TYPE:
>> + case UNION_TYPE:
>> + case ENUMERAL_TYPE:
>> + {
>> + /* Struct/union/enum: use simplified representation for C types. */
>> + const char *name = NULL;
>> +
>> + if (TYPE_NAME (type))
>> + {
>> + if (TREE_CODE (TYPE_NAME (type)) == TYPE_DECL)
>> + {
>> + /* TYPE_DECL case: both named structs and typedef structs.
>> */
>> + tree decl_name = DECL_NAME (TYPE_NAME (type));
>> + if (decl_name && TREE_CODE (decl_name) == IDENTIFIER_NODE)
>> + {
>> + name = IDENTIFIER_POINTER (decl_name);
>> + }
>> + }
>> + else if (TREE_CODE (TYPE_NAME (type)) == IDENTIFIER_NODE)
>> + {
>> + /* Direct identifier case. */
>> + name = IDENTIFIER_POINTER (TYPE_NAME (type));
>> + }
>> + }
>> +
>> + /* If no name found through normal extraction, handle anonymous
>> types following Itanium C++ ABI. */
>> + if (!name && !TYPE_NAME (type))
>> + {
>> + static char anon_name[128];
>> +
>> + if (TREE_CODE (type) == UNION_TYPE)
>> + {
>> + /* For anonymous unions, try to find first named field
>> (Itanium ABI approach). */
>> + tree field = TYPE_FIELDS (type);
>> + while (field && !DECL_NAME (field))
>> + field = DECL_CHAIN (field);
>> +
>> + if (field && DECL_NAME (field))
>> + {
>> + const char *field_name = IDENTIFIER_POINTER (DECL_NAME
>> (field));
>> + snprintf (anon_name, sizeof(anon_name),
>> "anon_union_by_%s", field_name);
>> + }
>> + else
>> + {
>> + /* No named fields - use Itanium-style Ut encoding. */
>> + snprintf (anon_name, sizeof(anon_name),
>> "Ut_unnamed_union");
>> + }
>> + }
>> + else
>> + {
>> + /* For anonymous structs/enums, use Itanium-style Ut
>> encoding with layout info for discrimination. */
>> + const char *type_prefix = "";
>> + if (TREE_CODE (type) == RECORD_TYPE)
>> + type_prefix = "struct";
>> + else if (TREE_CODE (type) == ENUMERAL_TYPE)
>> + type_prefix = "enum";
>> +
>> + /* Include size and field layout for better discrimination.
>> */
>> + HOST_WIDE_INT size = 0;
>> + if (TYPE_SIZE (type) && tree_fits_shwi_p (TYPE_SIZE (type)))
>> + size = tree_to_shwi (TYPE_SIZE (type));
>> +
>> + /* Generate a hash based on field layout to distinguish
>> same-sized anonymous types. */
>> + unsigned layout_hash = 0;
>> + if (TREE_CODE (type) == RECORD_TYPE)
>> + {
>> + for (tree field = TYPE_FIELDS (type); field; field =
>> DECL_CHAIN (field))
>> + {
>> + if (TREE_CODE (field) == FIELD_DECL)
>> + {
>> + /* Hash field offset and type. */
>> + if (DECL_FIELD_OFFSET (field))
>> + {
>> + HOST_WIDE_INT offset = tree_to_shwi
>> (DECL_FIELD_OFFSET (field));
>> + layout_hash = layout_hash * 31 +
>> (unsigned)offset;
>> + }
>> +
>> + /* Hash field type. */
>> + tree field_type = TREE_TYPE (field);
>> + if (field_type && TYPE_MODE (field_type) !=
>> VOIDmode)
>> + layout_hash = layout_hash * 37 +
>> (unsigned)TYPE_MODE (field_type);
>> + }
>> + }
>> + }
>> +
>> + if (layout_hash != 0)
>> + snprintf (anon_name, sizeof(anon_name), "Ut_%s_%ld_%x",
>> type_prefix, (long)size, layout_hash);
>> + else
>> + snprintf (anon_name, sizeof(anon_name), "Ut_%s_%ld",
>> type_prefix, (long)size);
>> + }
>> +
>> + name = anon_name;
>> + }
>> +
>> + if (name)
>> + {
>> + *p += snprintf (*p, end - *p, "%zu%s", strlen (name), name);
>> + }
>> + else
>> + {
>> + /* Always show diagnostic information for missing struct names.
>> */
>> + error ("mangle: No struct/union/enum name found for type code %d
>> (%qs)",
>> + TREE_CODE (type), get_tree_code_name (TREE_CODE (type)));
>> + if (TYPE_NAME (type))
>> + {
>> + error ("mangle: %<TYPE_NAME%> exists but extraction failed");
>> + error ("mangle: %<TYPE_NAME%> tree code = %d", TREE_CODE
>> (TYPE_NAME (type)));
>> + if (TREE_CODE (TYPE_NAME (type)) == TYPE_DECL)
>> + {
>> + tree decl_name = DECL_NAME (TYPE_NAME (type));
>> + error ("mangle: %<TYPE_DECL%> %<DECL_NAME%> = %p",
>> (void*)decl_name);
>> + if (decl_name && TREE_CODE (decl_name) ==
>> IDENTIFIER_NODE)
>> + error ("mangle: %<IDENTIFIER_NODE%> name = '%s'",
>> IDENTIFIER_POINTER (decl_name));
>> + }
>> + else if (TREE_CODE (TYPE_NAME (type)) == IDENTIFIER_NODE)
>> + {
>> + error ("mangle: %<IDENTIFIER_NODE%> name = '%s'",
>> IDENTIFIER_POINTER (TYPE_NAME (type)));
>> + }
>> + else
>> + {
>> + error ("mangle: Unknown %<TYPE_NAME%> tree code = %d",
>> TREE_CODE (TYPE_NAME (type)));
>> + }
>> + }
>> + else
>> + {
>> + error ("mangle: %<TYPE_NAME%> is NULL - anonymous
>> struct/union/enum detected");
>> + }
>> +
>> + /* This indicates a missing case in our struct name extraction.
>> */
>> + error ("mangle: Please report this as a bug with the above
>> diagnostic information");
>> + gcc_unreachable ();
>
>
> See above about sorry/fatal_error.
>
>>
>> + }
>> + break;
>> + }
>> +
>> + default:
>> + /* Handle builtin types. */
>> + mangle_builtin_type_to_buffer (type, p, end);
>> + break;
>> + }
>> +}
>> +
>> +/* Compute canonical type name using Itanium C++ ABI mangling.
>> + Accepts either FUNCTION_DECL (preferred for typedef preservation) or
>> FUNCTION_TYPE. */
>> +const char *
>> +mangle_function_type (tree fntype_or_fndecl)
>> +{
>> + gcc_assert (fntype_or_fndecl);
>> +
>> + tree fntype = NULL;
>> +
>> + /* Determine input type and extract function type. */
>> + if (TREE_CODE (fntype_or_fndecl) == FUNCTION_TYPE)
>> + {
>> + /* Already FUNCTION_TYPE. */
>> + fntype = fntype_or_fndecl;
>> + }
>> + else if (TREE_CODE (fntype_or_fndecl) == FUNCTION_DECL)
>> + {
>> + tree fndecl = fntype_or_fndecl;
>> + tree base_fntype = TREE_TYPE (fndecl);
>> +
>> + /* For FUNCTION_DECL, build a synthetic function type using
>> DECL_ARGUMENTS
>> + if available to preserve typedef information. */
>
>
> Why do the building? Seems like you could just do that work here. Also
> doesn't FUNCTION_DECL's type have exactly what you need?
>
>>
>> + tree parm = DECL_ARGUMENTS (fndecl);
>> + if (parm)
>> + {
>> + /* Build parameter type list from DECL_ARGUMENTS. */
>> + tree param_list = NULL_TREE;
>> + tree *param_tail = ¶m_list;
>> +
>> + for (; parm; parm = DECL_CHAIN (parm))
>> + {
>> + tree parm_type = TREE_TYPE (parm);
>> + *param_tail = tree_cons (NULL_TREE, parm_type, NULL_TREE);
>> + param_tail = &TREE_CHAIN (*param_tail);
>> + }
>> +
>> + /* Add void_type_node sentinel if the function takes no
>> parameters. */
>> + if (!param_list)
>> + param_list = tree_cons (NULL_TREE, void_type_node, NULL_TREE);
>> +
>> + /* Build synthetic function type with preserved parameter types.
>> */
>> + fntype = build_function_type (TREE_TYPE (base_fntype), param_list);
>> + }
>> + else
>> + {
>> + /* No DECL_ARGUMENTS - use the standard function type. */
>> + fntype = base_fntype;
>> + }
>> + }
>> + else
>> + {
>> + /* Must only be called with FUNCTION_DECL or FUNCTION_TYPE. */
>> + gcc_unreachable ();
>> + }
>> +
>> + static char name_buf[512];
>
>
> Why use a fixed size buffer on the stack? Why not use obstack or something to
> that extent. OR even std::string with a pre-allocated estimate.
>
> Thanks,
> Andrew
>
>>
>> + char *p = name_buf;
>> + char *end = name_buf + sizeof (name_buf) - 1;
>> +
>> + /* Typeinfo for a function prototype. */
>> + p += sprintf(name_buf, "_ZTSP");
>> +
>> + /* Use mangle_type_to_buffer for all cases. */
>> + mangle_type_to_buffer (fntype, &p, end);
>> +
>> + /* Ensure we didn't overflow the buffer. */
>> + gcc_assert (p <= end);
>> + *p = '\0';
>> + return name_buf;
>> +}
>> --
>> 2.34.1
>>
