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libbacktrace: support returning discriminator field

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Based on patch from Andi Kleen.

	* backtrace.h (backtrace_create_state): Rewrite comment to change
	threaded parameter to flags.
	(backtrace_full_callback, backtrace_syminfo_callback): Document
	behavior change if moredata flag is set.
	(struct backtrace_moredata): Define.
	* backtrace-supported.h.in (BACKTRACE_SUPPORTS_MOREDATA): Define.
	* internal.h (struct backtrace_state): Add moredata field.
	(BACKTRACE_MOREDATA_VERSION): Define.
	* state.c (backtrace_create_state): Change threaded parameter to
	flags.  Set state moredata field based on flags.
	* dwarf.c (struct line): Add disc field.
	(struct function): Add caller_disc field.
	(call_callback): New static function.
	(add_line): Add disc parameter.  Change all callers.  Store disc
	in new line value.
	(read_line_program): Track discriminator value.
	(read_line_info): Initialize disc field in final line entry.
	(read_function_entry): Handle DW_AT_GNU_discriminator.
	(report_inlined_functions): Add disc parameter. Change all
	callers. Call call_callback rather than calling callback
	directly.
	(dwarf_lookup_pc): Handle inlined discriminators. Call
	call_callback rather than calling callback directly.
	(dwarf_fileline): Call call_callback rather than calling callback
	directly.
	* elf.c (elf_syminfo): Pass moredata if requested.
	* macho.c (macho_syminfo): Likewise.
	* pecoff.c (coff_syminfo): Likewise.
	* xcoff.c (xcoff_syminfo): Likewise.
	(xcoff_lookup_pc): Likewise.
	* backtrace.c: #include <string.h>.
	(unwind): Pass moredata if requested.
	* unknown.c: #include <string.h>.
	(unknown_fileline): Pass moredata if requested.
	* fileline.c (backtrace_syminfo_to_full_callback): Add comment
	about moredata.
	* mdtest.c: New test file.
	* Makefile.am (mdtest_SOURCES): Define.
	(mdtest_CFLAGS, mdtest_LDFLAGS, mdtest_LDADD): Define.
	(BUILDTESTS): Add mdtest.
	* Makefile.in: Regenerate.
This commit is contained in:
Ian Lance Taylor
2026-07-06 12:42:21 -07:00
parent 5f4a6d4941
commit 6f8310e238
15 changed files with 635 additions and 75 deletions
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backtrace.h
+77 -21
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@@ -68,15 +68,41 @@ typedef void (*backtrace_error_callback) (void *data, const char *msg,
/* Create state information for the backtrace routines. This must be
called before any of the other routines, and its return value must
be passed to all of the other routines. FILENAME is the path name
of the executable file; if it is NULL the library will try
system-specific path names. If not NULL, FILENAME must point to a
permanent buffer. If THREADED is non-zero the state may be
accessed by multiple threads simultaneously, and the library will
use appropriate atomic operations. If THREADED is zero the state
may only be accessed by one thread at a time. This returns a state
pointer on success, NULL on error. If an error occurs, this will
call the ERROR_CALLBACK routine.
be passed to all of the other routines.
FILENAME is the path name of the executable file; if it is NULL the
library will try system-specific path names. If not NULL, FILENAME
must point to a permanent buffer.
FLAGS passes flags as bits in an int value:
1: THREADED
2: MOREDATA
If (FLAGS & 1) != 0 the THREADED flag is set. If this flag is set,
the state may be accessed by multiple threads simultaneously, and the
library will use appropriate atomic operations. If THREADED is not
set the state may only be accessed by one thread at a time.
If (FLAGS & 2) != 0 the MOREDATA flag is set. If this flag is set,
then backtrace_full_callback and backtrace_symbol_callback will not
pass the DATA argument as the user-specified DATA value, but will
instead pass it as a pointer to a backtrace_moredata struct. This is
a backward compatible approach to getting more data from the various
backtrace functions.
Historical note: in previous versions (before July, 2026) the FLAGS
argument was named THREADED, and passing non-zero for THREADED was
documented as doing what setting the THREADED flag does today. In
practice all callers passed either 0 or 1, so the new semantics of
the flag do not affect users of old versions of the library.
However, code that passes the MOREDATA flag must ensure that it is
using a new version of the library. The backtrace-supported.h file
will #define BACKTRACE_SUPPORTS_MOREDATA as 1 for versions of
libbacktrace that support the MOREDATA flag.
The backtrace_create_state function returns a state pointer on
success, NULL on error. If an error occurs, it will call the
ERROR_CALLBACK routine before returning.
Calling this function allocates resources that cannot be freed.
There is no backtrace_free_state function. The state is used to
@@ -89,13 +115,15 @@ extern struct backtrace_state *backtrace_create_state (
backtrace_error_callback error_callback, void *data);
/* The type of the callback argument to the backtrace_full function.
DATA is the argument passed to backtrace_full. PC is the program
counter. FILENAME is the name of the file containing PC, or NULL
if not available. LINENO is the line number in FILENAME containing
PC, or 0 if not available. FUNCTION is the name of the function
containing PC, or NULL if not available. This should return 0 to
continuing tracing. The FILENAME and FUNCTION buffers may become
invalid after this function returns. */
DATA is either the argument passed to backtrace_full (if the MOREDATA
flag was not set when calling backtrace_create_state) or a pointer to
a backtrace_moredata struct. PC is the program counter. FILENAME is
the name of the file containing PC, or NULL if not available. LINENO
is the line number in FILENAME containing PC, or 0 if not available.
FUNCTION is the name of the function containing PC, or NULL if not
available. This should return 0 to continuing tracing. The FILENAME
and FUNCTION buffers may become invalid after this function
returns. */
typedef int (*backtrace_full_callback) (void *data, uintptr_t pc,
const char *filename, int lineno,
@@ -156,11 +184,14 @@ extern int backtrace_pcinfo (struct backtrace_state *state, uintptr_t pc,
backtrace_error_callback error_callback,
void *data);
/* The type of the callback argument to backtrace_syminfo. DATA and
PC are the arguments passed to backtrace_syminfo. SYMNAME is the
name of the symbol for the corresponding code. SYMVAL is the
value and SYMSIZE is the size of the symbol. SYMNAME will be NULL
if no error occurred but the symbol could not be found. */
/* The type of the callback argument to backtrace_syminfo. DATA is
either the argument passed to backtrace_full (if the MOREDATA flag
was not set when calling backtrace_create_state) or a pointer to a
backtrace_moredata struct. PC is the the argument passed to
backtrace_syminfo. SYMNAME is the name of the symbol for the
corresponding code. SYMVAL is the value and SYMSIZE is the size of
the symbol. SYMNAME will be NULL if no error occurred but the symbol
could not be found. */
typedef void (*backtrace_syminfo_callback) (void *data, uintptr_t pc,
const char *symname,
@@ -182,6 +213,31 @@ extern int backtrace_syminfo (struct backtrace_state *state, uintptr_t addr,
backtrace_error_callback error_callback,
void *data);
/* The type of the value that the DATA argument passed to
backtrace_full_callback or backtrace_syminfo_callback points to if
the MOREDATA flag is set in the call to backtrace_create_state.
The backtrace_moredata value will only be valid for the lifetime of
the callback; the callback may copy the data out but must not save
the pointer it receives. */
struct backtrace_moredata
{
/* The version of this struct. The current expectation is that the
version number will be the number of fields in the struct. It's
possible that future versions of libbacktrace will add new fields
and increment the version number accordingly. There is no plan to
remove fields from this struct. Thus the current value of the
version field will be 3. */
int backtrace_version;
/* The DATA value passed to whatever function is calling the callback
(backtrace_full, backtrace_pcinfo, or backtrace_syminfo). */
void *backtrace_data;
/* The DWARF discriminator. This is zero if there is none. See
https://wiki.dwarfstd.org/Path_Discriminators.md. */
unsigned int backtrace_discriminator;
};
#ifdef __cplusplus
} /* End extern "C". */
#endif