[SFrame-V3] include: libsframe: remove SFRAME_F_FRAME_POINTER flag

SFrame V3 has 8 precious flag bits, two of which are being used.  More
flag byte (s) can be added to the auxiliary header when it comes to
that.  But for now, it may be worthwhile to use the 8-bits frugally.

SFRAME_F_FRAME_POINTER flag bit was added with the intention of marking
binaries built with frame-pointer preserved.  A stack tracer could then
use this information, to unambiguously ascertain whether frame-pointer
based stack traces will be precise.  But such a marking of binary will
ideally be done by the linker, and at the moment adding such a framework
is not justified for such small gain.  The outcome of this is that
SFRAME_F_FRAME_POINTER is never set in SFrame V2 binaries.

Remove the definition SFRAME_F_FRAME_POINTER for SFrame V3.  The
relinquished bit can be used (in future format incarnations) when
reading/dumping SFrame V2 sections are no longer supported by consumers.
Changing the values of existing flags, e.g.,
SFRAME_F_FDE_FUNC_START_PCREL, is not being done for V3, to avoid
version-specific flag bit reading (albeit doable) in consumers.

Related changes to the specification are done in a subsequent commit.

include/
	* sframe.h (SFRAME_V3_F_ALL_FLAGS): Remove
	SFRAME_F_FRAME_POINTER from the set of V3 flags.
libsframe/
	* sframe-dump.c (dump_sframe_header_flags): Add a comment for
	clarity.

diff --git a/include/sframe.h b/include/sframe.h
index f1409d3626360f50b4e969a13ea23ebf9575c3aa..1c026d514728ebd6404df2ce934f917608b396ec 100644 (file)
--- a/include/sframe.h
+++ b/include/sframe.h
@@ -100,8 +100,7 @@ extern "C"
 
 /* Set of all defined flags in SFrame V3.  */
 #define SFRAME_V3_F_ALL_FLAGS \
-  (SFRAME_F_FDE_SORTED | SFRAME_F_FRAME_POINTER \
-   | SFRAME_F_FDE_FUNC_START_PCREL)
+  (SFRAME_F_FDE_SORTED | SFRAME_F_FDE_FUNC_START_PCREL)
 
 #define SFRAME_CFA_FIXED_FP_INVALID 0
 #define SFRAME_CFA_FIXED_RA_INVALID 0

diff --git a/libsframe/sframe-dump.c b/libsframe/sframe-dump.c
index 9f7c6cfa8985ef26e6c8d7b30fb56de16c6eded0..742b60b6f4f8c29501680386092ceb4fc5081f68 100644 (file)
--- a/libsframe/sframe-dump.c
+++ b/libsframe/sframe-dump.c
@@ -119,10 +119,11 @@ is_sframe_abi_arch_s390x (const sframe_decoder_ctx *sfd_ctx)
 static void
 dump_sframe_header_flags (const sframe_decoder_ctx *sfd_ctx)
 {
-  uint8_t flags;
   const char *prefix = "Flags: ";
 
-  flags = sframe_decoder_get_flags (sfd_ctx);
+  uint8_t ver = sframe_decoder_get_version (sfd_ctx);
+  uint8_t flags = sframe_decoder_get_flags (sfd_ctx);
+
   if (!flags)
     {
       printf ("%11sNONE\n", prefix);
@@ -137,7 +138,9 @@ dump_sframe_header_flags (const sframe_decoder_ctx *sfd_ctx)
     }
 
   PRINT_FLAG (SFRAME_F_FDE_SORTED);
-  PRINT_FLAG (SFRAME_F_FRAME_POINTER);
+  /* SFRAME_F_FRAME_POINTER has been removed from SFrame V3 and beyond.  */
+  if (ver == SFRAME_VERSION_2)
+    PRINT_FLAG (SFRAME_F_FRAME_POINTER);
   PRINT_FLAG (SFRAME_F_FDE_FUNC_START_PCREL);
 #undef PRINT_FLAG