[PATCH 6/6] gdb/record: Define new version of the record-save section

Guinevere Larsen
2026-04-15T19:00:44Z

With the changes to the internal representation of the history, we can
no longer support the previous record save format. This commit makes it
official, documenting the new format and changing the magic number.
---
gdb/NEWS | 3 +++
gdb/record-full.c | 35 +++++++++++++++++++++++++++++++----
2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 4cf91053c95..4380a394376 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -42,6 +42,9 @@

* Support for the binary file format dbx has been removed.

+* The format for a saved execution record has been updated, and
+ previous formats are no longer supported.
+
* When connected to an extended-remote target GDB can now
automatically set the 'remote exec-file' in some cases. GDB will
auto set the remote exec-file only if the remote wasn't started with
diff --git a/gdb/record-full.c b/gdb/record-full.c
index 297b5b76ae7..f7cfe5ca1e9 100644
--- a/gdb/record-full.c
+++ b/gdb/record-full.c
@@ -76,7 +76,8 @@
( (record_full_next_insn != record_full_list.size ()) \
|| ::execution_direction == EXEC_REVERSE)

-#define RECORD_FULL_FILE_MAGIC netorder32(0x20091016)
+#define RECORD_FULL_FILE_MAGIC_OLD netorder32(0x20091016)
+#define RECORD_FULL_FILE_MAGIC netorder32(0x20260415)

/* These are the core structs of the process record functionality.

@@ -2161,6 +2162,27 @@ record_full_core_target::has_execution (inferior *inf)
8 bytes: memory address (network byte order).
n bytes: memory value (n == memory length).

+ Version 3 (all numbers are in network order).
+ 4 bytes: Magic number (0x20260415).
+ NOTE: be sure to change whenever this file format changes!
+
+ Records:
+ record_full_instruction:
+ 4 bytes: number of reg and mem entries for this instruction.
+ 1 byte: signal.
+ 4 bytes: instruction count.
+ 4 bytes: PC register ID.
+ N bytes: PC address of instruction (N == size of PC).
+ Effects:
+ record_full_reg:
+ 1 byte: record_type (record_full_reg, see enum record_full_type).
+ 4 bytes: Register ID.
+ n bytes: register value (n == actual register size).
+ record_full_mem:
+ 1 byte: record_type (record_full_mem, see enum record_full_type).
+ 4 bytes: memory length.
+ 8 bytes: memory address.
+ n bytes: memory value (n = memory length).
*/

/* bfdcore_read -- read bytes from a core file section. */
@@ -2323,9 +2345,14 @@ record_full_restore (struct bfd &cbfd)
/* Check the magic code. */
bfdcore_read (&cbfd, osec, &magic, sizeof (magic), &bfd_offset);
if (magic != RECORD_FULL_FILE_MAGIC)
- error (_("Version mismatch or file format error in core file %ps."),
- styled_string (file_name_style.style (),
- bfd_get_filename (&cbfd)));
+ {
+ if (magic == RECORD_FULL_FILE_MAGIC_OLD)
+ error (_("This old recording format is no longer supported."));
+ else
+ error (_("Version mismatch or file format error in core file %ps."),
+ styled_string (file_name_style.style (),
+ bfd_get_filename (&cbfd)));
+ }
if (record_debug)
gdb_printf (gdb_stdlog,
" Reading 4-byte magic cookie "
--
2.53.0