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Re: [RFA 1/2] Move ptype/o printing code to typeprint.c
On Saturday, June 23 2018, Tom Tromey wrote:
> This moves the hole-printing support code for ptype/o from
> c-typeprint.c to be methods on print_offset_data. This allows the
> code to be used from non-C languages.
Thanks, Tom. I looked at the patch, and it seems OK to me. Just one
small nit.
> gdb/ChangeLog
> 2018-06-08 Tom Tromey <tom@tromey.com>
>
> * typeprint.h (struct print_offset_data) <update, finish,
> maybe_print_hole>: New methods.
> <indentation>: New constant.
> * typeprint.c (print_offset_data::indentation): Define.
> (print_offset_data::maybe_print_hole, print_offset_data::update)
> (print_offset_data::finish): Move from c-typeprint.c and rename.
> * c-typeprint.c (OFFSET_SPC_LEN): Remove.
> (print_spaces_filtered_with_print_options): Update.
> (c_print_type_union_field_offset, maybe_print_hole)
> (c_print_type_struct_field_offset): Move to typeprint.c and
> rename.
> (c_type_print_base_struct_union): Update.
> ---
> gdb/ChangeLog | 15 +++++
> gdb/c-typeprint.c | 160 ++----------------------------------------------------
> gdb/typeprint.c | 122 +++++++++++++++++++++++++++++++++++++++++
> gdb/typeprint.h | 33 +++++++++++
> 4 files changed, 174 insertions(+), 156 deletions(-)
>
> diff --git a/gdb/c-typeprint.c b/gdb/c-typeprint.c
> index d7eaa5433dd..c167e212ded 100644
> --- a/gdb/c-typeprint.c
> +++ b/gdb/c-typeprint.c
> @@ -32,14 +32,6 @@
> #include "cp-abi.h"
> #include "cp-support.h"
>
> -/* When printing the offsets of a struct and its fields (i.e., 'ptype
> - /o'; type_print_options::print_offsets), we use this many
> - characters when printing the offset information at the beginning of
> - the line. This is needed in order to generate the correct amount
> - of whitespaces when no offset info should be printed for a certain
> - field. */
> -#define OFFSET_SPC_LEN 23
> -
> /* A list of access specifiers used for printing. */
>
> enum access_specifier
> @@ -913,7 +905,7 @@ print_spaces_filtered_with_print_options
> if (!flags->print_offsets)
> print_spaces_filtered (level, stream);
> else
> - print_spaces_filtered (level + OFFSET_SPC_LEN, stream);
> + print_spaces_filtered (level + print_offset_data::indentation, stream);
> }
>
> /* Output an access specifier to STREAM, if needed. LAST_ACCESS is the
> @@ -956,127 +948,6 @@ output_access_specifier (struct ui_file *stream,
> return last_access;
> }
>
> -/* Print information about field at index FIELD_IDX of the union type
> - TYPE. Since union fields don't have the concept of offsets, we
> - just print their sizes.
> -
> - The output is strongly based on pahole(1). */
> -
> -static void
> -c_print_type_union_field_offset (struct type *type, unsigned int field_idx,
> - struct ui_file *stream)
> -{
> - struct type *ftype = check_typedef (TYPE_FIELD_TYPE (type, field_idx));
> -
> - fprintf_filtered (stream, "/* %4u */", TYPE_LENGTH (ftype));
> -}
> -
> -/* Helper function for ptype/o implementation that prints information
> - about a hole, if necessary. STREAM is where to print. BITPOS is
> - the bitpos of the current field. PODATA is the offset-printing
> - state. FOR_WHAT is a string describing the purpose of the
> - hole. */
> -
> -static void
> -maybe_print_hole (struct ui_file *stream, unsigned int bitpos,
> - struct print_offset_data *podata, const char *for_what)
> -{
> - /* We check for PODATA->END_BITPOS > 0 because there is a specific
> - scenario when PODATA->END_BITPOS can be zero and BITPOS can be >
> - 0: when we are dealing with a struct/class with a virtual method.
> - Because of the vtable, the first field of the struct/class will
> - have an offset of sizeof (void *) (the size of the vtable). If
> - we do not check for PODATA->END_BITPOS > 0 here, GDB will report
> - a hole before the first field, which is not accurate. */
> - if (podata->end_bitpos > 0 && podata->end_bitpos < bitpos)
> - {
> - /* If PODATA->END_BITPOS is smaller than the current type's
> - bitpos, it means there's a hole in the struct, so we report
> - it here. */
> - unsigned int hole = bitpos - podata->end_bitpos;
> - unsigned int hole_byte = hole / TARGET_CHAR_BIT;
> - unsigned int hole_bit = hole % TARGET_CHAR_BIT;
> -
> - if (hole_bit > 0)
> - fprintf_filtered (stream, "/* XXX %2u-bit %s */\n", hole_bit,
> - for_what);
> -
> - if (hole_byte > 0)
> - fprintf_filtered (stream, "/* XXX %2u-byte %s */\n", hole_byte,
> - for_what);
> - }
> -}
> -
> -/* Print information about field at index FIELD_IDX of the struct type
> - TYPE.
> -
> - PODATA->END_BITPOS is the one-past-the-end bit position of the
> - previous field (where we expect this field to be if there is no
> - hole). At the end, ENDPOS is updated to the one-past-the-end bit
> - position of the current field.
> -
> - PODATA->OFFSET_BITPOS is the offset value we carry over when we are
> - printing a struct that is inside another struct; this is useful so
> - that the offset is constantly incremented (if we didn't carry it
> - over, the offset would be reset to zero when printing the inner
> - struct).
> -
> - The output is strongly based on pahole(1). */
> -
> -static void
> -c_print_type_struct_field_offset (struct type *type, unsigned int field_idx,
> - struct ui_file *stream,
> - struct print_offset_data *podata)
> -{
> - struct type *ftype = check_typedef (TYPE_FIELD_TYPE (type, field_idx));
> - unsigned int bitpos = TYPE_FIELD_BITPOS (type, field_idx);
> - unsigned int fieldsize_byte = TYPE_LENGTH (ftype);
> - unsigned int fieldsize_bit = fieldsize_byte * TARGET_CHAR_BIT;
> -
> - maybe_print_hole (stream, bitpos, podata, "hole");
> -
> - if (TYPE_FIELD_PACKED (type, field_idx))
> - {
> - /* We're dealing with a bitfield. Print how many bits are left
> - to be used. */
> - unsigned int bitsize = TYPE_FIELD_BITSIZE (type, field_idx);
> - /* The bitpos relative to the beginning of our container
> - field. */
> - unsigned int relative_bitpos;
> -
> - /* The following was copied from
> - value.c:value_primitive_field. */
> - if ((bitpos % fieldsize_bit) + bitsize <= fieldsize_bit)
> - relative_bitpos = bitpos % fieldsize_bit;
> - else
> - relative_bitpos = bitpos % TARGET_CHAR_BIT;
> -
> - /* This is the exact offset (in bits) of this bitfield. */
> - unsigned int bit_offset
> - = (bitpos - relative_bitpos) + podata->offset_bitpos;
> -
> - /* The position of the field, relative to the beginning of the
> - struct, and how many bits are left to be used in this
> - container. */
> - fprintf_filtered (stream, "/* %4u:%2u", bit_offset / TARGET_CHAR_BIT,
> - fieldsize_bit - (relative_bitpos + bitsize));
> - fieldsize_bit = bitsize;
> - }
> - else
> - {
> - /* The position of the field, relative to the beginning of the
> - struct. */
> - fprintf_filtered (stream, "/* %4u",
> - (bitpos + podata->offset_bitpos) / TARGET_CHAR_BIT);
> -
> - fprintf_filtered (stream, " ");
> - }
> -
> - fprintf_filtered (stream, " | %4u */", fieldsize_byte);
> -
> - podata->end_bitpos = bitpos + fieldsize_bit;
> -}
> -
> /* Return true if an access label (i.e., "public:", "private:",
> "protected:") needs to be printed for TYPE. */
>
> @@ -1289,20 +1160,7 @@ c_type_print_base_struct_union (struct type *type, struct ui_file *stream,
> bool is_static = field_is_static (&TYPE_FIELD (type, i));
>
> if (flags->print_offsets)
> - {
> - if (!is_static)
> - {
> - if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
> - {
> - c_print_type_struct_field_offset
> - (type, i, stream, podata);
> - }
> - else if (TYPE_CODE (type) == TYPE_CODE_UNION)
> - c_print_type_union_field_offset (type, i, stream);
> - }
> - else
> - print_spaces_filtered (OFFSET_SPC_LEN, stream);
> - }
> + podata->update (type, i, stream);
>
> print_spaces_filtered (level + 4, stream);
> if (is_static)
> @@ -1560,19 +1418,9 @@ c_type_print_base_struct_union (struct type *type, struct ui_file *stream,
> if (flags->print_offsets)
> {
> if (show > 0)
> - {
> - unsigned int bitpos = TYPE_LENGTH (type) * TARGET_CHAR_BIT;
> - maybe_print_hole (stream, bitpos, podata, "padding");
> -
> - fputs_filtered ("\n", stream);
> - print_spaces_filtered_with_print_options (level + 4,
> - stream,
> - flags);
> - fprintf_filtered (stream, "/* total size (bytes): %4u */\n",
> - TYPE_LENGTH (type));
> - }
> + podata->finish (type, level, stream);
>
> - print_spaces_filtered (OFFSET_SPC_LEN, stream);
> + print_spaces_filtered (print_offset_data::indentation, stream);
> if (level == 0)
> print_spaces_filtered (2, stream);
> }
> diff --git a/gdb/typeprint.c b/gdb/typeprint.c
> index 222fc0a06b1..66ba0a87c6a 100644
> --- a/gdb/typeprint.c
> +++ b/gdb/typeprint.c
> @@ -65,6 +65,128 @@ static struct type_print_options default_ptype_flags =
>
>
>
> +const int print_offset_data::indentation = 23;
A "/* See typeprint.h. */" comment would be nice here, IMO.
> +
> +
> +/* See typeprint.h. */
> +
> +void
> +print_offset_data::maybe_print_hole (struct ui_file *stream,
> + unsigned int bitpos,
> + const char *for_what)
> +{
> + /* We check for END_BITPOS > 0 because there is a specific
> + scenario when END_BITPOS can be zero and BITPOS can be >
> + 0: when we are dealing with a struct/class with a virtual method.
> + Because of the vtable, the first field of the struct/class will
> + have an offset of sizeof (void *) (the size of the vtable). If
> + we do not check for END_BITPOS > 0 here, GDB will report
> + a hole before the first field, which is not accurate. */
> + if (end_bitpos > 0 && end_bitpos < bitpos)
> + {
> + /* If END_BITPOS is smaller than the current type's
> + bitpos, it means there's a hole in the struct, so we report
> + it here. */
> + unsigned int hole = bitpos - end_bitpos;
> + unsigned int hole_byte = hole / TARGET_CHAR_BIT;
> + unsigned int hole_bit = hole % TARGET_CHAR_BIT;
> +
> + if (hole_bit > 0)
> + fprintf_filtered (stream, "/* XXX %2u-bit %s */\n", hole_bit,
> + for_what);
> +
> + if (hole_byte > 0)
> + fprintf_filtered (stream, "/* XXX %2u-byte %s */\n", hole_byte,
> + for_what);
> + }
> +}
> +
> +/* See typeprint.h. */
> +
> +void
> +print_offset_data::update (struct type *type, unsigned int field_idx,
> + struct ui_file *stream)
> +{
> + if (field_is_static (&TYPE_FIELD (type, field_idx)))
> + {
> + print_spaces_filtered (indentation, stream);
> + return;
> + }
> +
> + struct type *ftype = check_typedef (TYPE_FIELD_TYPE (type, field_idx));
> + if (TYPE_CODE (type) == TYPE_CODE_UNION)
> + {
> + /* Since union fields don't have the concept of offsets, we just
> + print their sizes. */
> + fprintf_filtered (stream, "/* %4u */", TYPE_LENGTH (ftype));
> + return;
> + }
> +
> + unsigned int bitpos = TYPE_FIELD_BITPOS (type, field_idx);
> + unsigned int fieldsize_byte = TYPE_LENGTH (ftype);
> + unsigned int fieldsize_bit = fieldsize_byte * TARGET_CHAR_BIT;
> +
> + maybe_print_hole (stream, bitpos, "hole");
> +
> + if (TYPE_FIELD_PACKED (type, field_idx))
> + {
> + /* We're dealing with a bitfield. Print how many bits are left
> + to be used. */
> + unsigned int bitsize = TYPE_FIELD_BITSIZE (type, field_idx);
> + /* The bitpos relative to the beginning of our container
> + field. */
> + unsigned int relative_bitpos;
> +
> + /* The following was copied from
> + value.c:value_primitive_field. */
> + if ((bitpos % fieldsize_bit) + bitsize <= fieldsize_bit)
> + relative_bitpos = bitpos % fieldsize_bit;
> + else
> + relative_bitpos = bitpos % TARGET_CHAR_BIT;
> +
> + /* This is the exact offset (in bits) of this bitfield. */
> + unsigned int bit_offset
> + = (bitpos - relative_bitpos) + offset_bitpos;
> +
> + /* The position of the field, relative to the beginning of the
> + struct, and how many bits are left to be used in this
> + container. */
> + fprintf_filtered (stream, "/* %4u:%2u", bit_offset / TARGET_CHAR_BIT,
> + fieldsize_bit - (relative_bitpos + bitsize));
> + fieldsize_bit = bitsize;
> + }
> + else
> + {
> + /* The position of the field, relative to the beginning of the
> + struct. */
> + fprintf_filtered (stream, "/* %4u",
> + (bitpos + offset_bitpos) / TARGET_CHAR_BIT);
> +
> + fprintf_filtered (stream, " ");
> + }
> +
> + fprintf_filtered (stream, " | %4u */", fieldsize_byte);
> +
> + end_bitpos = bitpos + fieldsize_bit;
> +}
> +
> +/* See typeprint.h. */
> +
> +void
> +print_offset_data::finish (struct type *type, int level,
> + struct ui_file *stream)
> +{
> + unsigned int bitpos = TYPE_LENGTH (type) * TARGET_CHAR_BIT;
> + maybe_print_hole (stream, bitpos, "padding");
> +
> + fputs_filtered ("\n", stream);
> + print_spaces_filtered (level + 4 + print_offset_data::indentation, stream);
> + fprintf_filtered (stream, "/* total size (bytes): %4u */\n",
> + TYPE_LENGTH (type));
> +}
> +
> +
> +
> /* A hash function for a typedef_field. */
>
> static hashval_t
> diff --git a/gdb/typeprint.h b/gdb/typeprint.h
> index 74006b3058f..edd8c396c87 100644
> --- a/gdb/typeprint.h
> +++ b/gdb/typeprint.h
> @@ -38,6 +38,39 @@ struct print_offset_data
> field (where we expect the current field to be if there is no
> hole). */
> unsigned int end_bitpos = 0;
> +
> + /* Print information about field at index FIELD_IDX of the struct type
> + TYPE and update this object.
> +
> + If the field is static, it simply prints the correct number of
> + spaces.
> +
> + The output is strongly based on pahole(1). */
> + void update (struct type *type, unsigned int field_idx,
> + struct ui_file *stream);
> +
> + /* Call when all fields have been printed. This will print
> + information about any padding that may exist. LEVEL is the
> + desired indentation level. */
> + void finish (struct type *type, int level, struct ui_file *stream);
> +
> + /* When printing the offsets of a struct and its fields (i.e.,
> + 'ptype /o'; type_print_options::print_offsets), we use this many
> + characters when printing the offset information at the beginning
> + of the line. This is needed in order to generate the correct
> + amount of whitespaces when no offset info should be printed for a
> + certain field. */
> + static const int indentation;
> +
> +private:
> +
> + /* Helper function for ptype/o implementation that prints
> + information about a hole, if necessary. STREAM is where to
> + print. BITPOS is the bitpos of the current field. FOR_WHAT is a
> + string describing the purpose of the hole. */
> +
> + void maybe_print_hole (struct ui_file *stream, unsigned int bitpos,
> + const char *for_what);
> };
>
> struct type_print_options
> --
> 2.13.6
--
Sergio
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