[PATCH] gdb: Print frame address in more cases
Christian Biesinger via gdb-patches
gdb-patches@sourceware.org
Wed Mar 4 19:54:00 GMT 2020
On Wed, Mar 4, 2020 at 8:13 AM Andrew Burgess
<andrew.burgess@embecosm.com> wrote:
>
> Change GDB to display the frame address for all inline frames except
> the inner most frame. This issue was discussed briefly on the mailing
> list here:
>
> https://sourceware.org/ml/gdb-patches/2019-12/msg01015.html
Thanks! I think this makes more sense.
Christian
> Consider this stack setup from the test gdb.dwarf2/dw2-inline-many-frames.exp:
>
> #11 #10 #9 #8 #7 #6 #5 #4 #3 #2 #1 #0
> main -> aaa -> bbb -> ccc -> ddd -> eee -> fff -> ggg -> hhh -> iii -> jjj -> kkk
> \_______________________/ \________/ \______________________/ \________/
> Inline sequence #1 Normal Inline sequence #2 Normal
>
> When we stop in GDB and backtrace the stack is displayed like
> this (I've replaced the file and line information with "..."):
>
> (gdb) bt
> #0 kkk () at ...
> #1 0x0000000000400494 in jjj () at ...
> #2 0x00000000004004b1 in iii () at ...
> #3 hhh () at ...
> #4 ggg () at ...
> #5 fff () at ...
> #6 0x0000000000400536 in eee () at ...
> #7 0x0000000000400519 in ddd () at ...
> #8 0x00000000004004f3 in ccc () at ...
> #9 bbb () at ...
> #10 aaa () at ...
> #11 main () at ...
> (gdb)
>
> Notice that many frames are missing an address, take the sequence for
> frames #6 to #2. Frame #6 is a non-inline frame and has an address.
> Frame #6 calls to frame #5 which is also non-inline. Frames #4, #3,
> and #2 are all inline within frame #5, and of these only frame #2 has
> an address displayed.
>
> This lack of address can be confusing, there's no clear indication why
> the addresses are missing, a user needs to understand that the missing
> address implies an inline frame, and can then infer the address based
> on the address of frame #2.
>
> After this patch the backtrace is now show like this:
>
> #0 kkk () at ...
> #1 0x0000000000400494 in jjj () at ...
> #2 0x00000000004004b1 in iii () at ...
> #3 0x00000000004004b1 in hhh () at ...
> #4 0x00000000004004b1 in ggg () at ...
> #5 0x00000000004004b1 in fff () at ...
> #6 0x0000000000400536 in eee () at ...
> #7 0x0000000000400519 in ddd () at ...
> #8 0x00000000004004f3 in ccc () at ...
> #9 0x00000000004004f3 in bbb () at ...
> #10 0x00000000004004f3 in aaa () at ...
> #11 0x00000000004004f3 in main () at ...
>
> Now all frames (except #0) have an address. Frames that are inline,
> and previously lacked an address will now have the same address as the
> inner-most inline frame in the sequence, so for the inline sequence #5
> to #2, all frames have the same address as frame #2. For the sequence
> frame #11 to #8, all have the address of frame #8.
>
> The duplicated address might also be confusing, though (personally) I
> think it is slightly more obvious from the duplicated addresses that
> the frames are inlined, however, if people strongly disagree and
> prefer the no-address layout we could make this feature switchable.
>
> One further location where the no address can crop up, is when the
> user switches frame, previously we would see:
>
> (gdb) frame 3
> #3 hhh () at ...
> 115 return iii () + 1;
> (gdb)
>
> After the patch we see:
>
> (gdb) frame 3
> #3 0x00000000004004b1 in hhh () at ...
> 115 return iii () + 1;
> (gdb)
>
> There were a small number of tests that needed to have their expected
> results updated, and I added a small section to the documentation to
> help users understand what duplicate addresses in the backtrace might
> mean.
>
> gdb/ChangeLog:
>
> * stack.c (frame_show_address): Show the frame address for all but
> the inner-most inlined frame.
>
> gdb/testsuite/ChangeLog:
>
> * gdb.dwarf2/dw2-inline-many-frames.exp: Update expected results.
> * gdb.dwarf2/dw2-inline-param.exp: Likewise.
> * gdb.guile/scm-frame-inline.exp: Likewise.
> * gdb.opt/inline-cmds.exp: Likewise.
> * gdb.python/py-frame-inline.exp: Likewise.
>
> gdb/doc/ChangeLog:
>
> * gdb.texinfo (Backtrace): Mention duplicate addresses in the
> backtrace.
> ---
> gdb/ChangeLog | 5 +++++
> gdb/doc/ChangeLog | 5 +++++
> gdb/doc/gdb.texinfo | 18 ++++++++++++++++++
> gdb/stack.c | 2 +-
> gdb/testsuite/ChangeLog | 8 ++++++++
> gdb/testsuite/gdb.dwarf2/dw2-inline-many-frames.exp | 12 ++++++------
> gdb/testsuite/gdb.dwarf2/dw2-inline-param.exp | 4 +++-
> gdb/testsuite/gdb.guile/scm-frame-inline.exp | 2 +-
> gdb/testsuite/gdb.opt/inline-cmds.exp | 14 +++++++-------
> gdb/testsuite/gdb.python/py-frame-inline.exp | 6 +++---
> 10 files changed, 57 insertions(+), 19 deletions(-)
>
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 32e419ead02..74178faee37 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -8013,6 +8013,24 @@
> either deduce that from other variables whose values depend on the one
> you are interested in, or recompile without optimizations.
>
> +If your compiler has performed the function inlining optimisation
> +(@pxref{Inline Functions}) then this will be reflected in the program
> +counter addresses displayed in the backtrace. In the following
> +modified example the function @code{expand_macro} has been inlined
> +within @code{expand_token}, as a result the program counter values for
> +frame 1 and frame 2 are the same.
> +
> +@smallexample
> +@group
> +#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
> + at builtin.c:993
> +#1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
> +#2 0x6e38 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
> + at macro.c:71
> +(More stack frames follow...)
> +@end group
> +@end smallexample
> +
> @cindex backtrace beyond @code{main} function
> @cindex program entry point
> @cindex startup code, and backtrace
> diff --git a/gdb/stack.c b/gdb/stack.c
> index 266d771e35f..4570eed1a2f 100644
> --- a/gdb/stack.c
> +++ b/gdb/stack.c
> @@ -327,7 +327,7 @@ frame_show_address (struct frame_info *frame,
> gdb_assert (inline_skipped_frames (inferior_thread ()) > 0);
> else
> gdb_assert (get_frame_type (get_next_frame (frame)) == INLINE_FRAME);
> - return false;
> + return frame_relative_level (frame) > 0;
> }
>
> return get_frame_pc (frame) != sal.pc;
> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-inline-many-frames.exp b/gdb/testsuite/gdb.dwarf2/dw2-inline-many-frames.exp
> index 146af8c6ef7..f5890fb2aca 100644
> --- a/gdb/testsuite/gdb.dwarf2/dw2-inline-many-frames.exp
> +++ b/gdb/testsuite/gdb.dwarf2/dw2-inline-many-frames.exp
> @@ -350,15 +350,15 @@ gdb_test "bt" [multi_line \
> "#0 kkk \\(\\) at \[^\r\n\]+${srcfile}:${line_in_kkk}" \
> "#1 $hex in jjj \\(\\) at \[^\r\n\]+${srcfile}:${line_in_jjj}" \
> "#2 $hex in iii \\(\\) at \[^\r\n\]+${srcfile}:${line_in_iii}" \
> - "#3 hhh \\(\\) at \[^\r\n\]+${srcfile}:${line_in_hhh}" \
> - "#4 ggg \\(\\) at \[^\r\n\]+${srcfile}:${line_in_ggg}" \
> - "#5 fff \\(\\) at \[^\r\n\]+${srcfile}:${line_in_fff}" \
> + "#3 $hex in hhh \\(\\) at \[^\r\n\]+${srcfile}:${line_in_hhh}" \
> + "#4 $hex in ggg \\(\\) at \[^\r\n\]+${srcfile}:${line_in_ggg}" \
> + "#5 $hex in fff \\(\\) at \[^\r\n\]+${srcfile}:${line_in_fff}" \
> "#6 $hex in eee \\(\\) at \[^\r\n\]+${srcfile}:${line_in_eee}" \
> "#7 $hex in ddd \\(\\) at \[^\r\n\]+${srcfile}:${line_in_ddd}" \
> "#8 $hex in ccc \\(\\) at \[^\r\n\]+${srcfile}:${line_in_ccc}" \
> - "#9 bbb \\(\\) at \[^\r\n\]+${srcfile}:${line_in_bbb}" \
> - "#10 aaa \\(\\) at \[^\r\n\]+${srcfile}:${line_in_aaa}" \
> - "#11 main \\(\\) at \[^\r\n\]+${srcfile}:${line_in_main}" ]
> + "#9 $hex in bbb \\(\\) at \[^\r\n\]+${srcfile}:${line_in_bbb}" \
> + "#10 $hex in aaa \\(\\) at \[^\r\n\]+${srcfile}:${line_in_aaa}" \
> + "#11 $hex in main \\(\\) at \[^\r\n\]+${srcfile}:${line_in_main}" ]
>
> # Now check we can use 'up' to inspect each frame correctly.
> set patterns [list \
> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-inline-param.exp b/gdb/testsuite/gdb.dwarf2/dw2-inline-param.exp
> index 1c1e75619da..e27ef8f3b38 100644
> --- a/gdb/testsuite/gdb.dwarf2/dw2-inline-param.exp
> +++ b/gdb/testsuite/gdb.dwarf2/dw2-inline-param.exp
> @@ -55,4 +55,6 @@ if ![runto "*${break_at}"] {
> return -1
> }
>
> -gdb_test "bt" "#0 (0x\[0-9a-f\]+ in )?func \\(funcparam=<optimized out>\\)\r\n#1 main \\(mainparam=<optimized out>\\)\[^\r\n\]*"
> +gdb_test "bt" [multi_line \
> + "#0 ($hex in )?func \\(funcparam=<optimized out>\\)" \
> + "#1 $hex in main \\(mainparam=<optimized out>\\)\[^\r\n\]*" ]
> diff --git a/gdb/testsuite/gdb.guile/scm-frame-inline.exp b/gdb/testsuite/gdb.guile/scm-frame-inline.exp
> index 8a4d8f893de..70882f841d7 100644
> --- a/gdb/testsuite/gdb.guile/scm-frame-inline.exp
> +++ b/gdb/testsuite/gdb.guile/scm-frame-inline.exp
> @@ -37,7 +37,7 @@ gdb_continue_to_breakpoint "break-here"
>
> gdb_test "info frame" "inlined into frame 1\r\n.*"
>
> -gdb_test "up" "#1 g .*"
> +gdb_test "up" "#1 $hex in g .*"
>
> gdb_test "guile (print (frame-read-var (selected-frame) \"l\"))" \
> "= 42"
> diff --git a/gdb/testsuite/gdb.opt/inline-cmds.exp b/gdb/testsuite/gdb.opt/inline-cmds.exp
> index aa8c8c6bfa0..de5eb1dfee5 100644
> --- a/gdb/testsuite/gdb.opt/inline-cmds.exp
> +++ b/gdb/testsuite/gdb.opt/inline-cmds.exp
> @@ -288,15 +288,15 @@ gdb_test_multiple "finish" "finish from marker" {
> }
> gdb_test "bt" "#0 main.*" "backtrace at main of outer_inline"
> gdb_test "step" "outer_inline2 \\\(\\\) at .*" "enter outer_inline2"
> -gdb_test "bt" "#0 outer_inline2.*#1 main.*" "backtrace at outer_inline2"
> +gdb_test "bt" "#0 outer_inline2.*#1 $hex in main.*" "backtrace at outer_inline2 xx"
> gdb_test "step" "outer_inline1 \\\(\\\) at .*" "enter outer_inline1 from outer_inline2"
>
> set msg "backtrace at outer_inline1"
> gdb_test_multiple "bt" $msg {
> - -re "#0 outer_inline1.*#1 outer_inline2.*#2 main.*$gdb_prompt $" {
> + -re "#0 outer_inline1.*#1 $hex in outer_inline2.*#2 $hex in main.*$gdb_prompt $" {
> pass $msg
> }
> - -re "#0 $hex in outer_inline1.*#1 outer_inline2.*#2 main.*$gdb_prompt $" {
> + -re "#0 $hex in outer_inline1.*#1 $hex in outer_inline2.*#2 $hex in main.*$gdb_prompt $" {
> # Binutils PR gas/6717. Gas moves .loc past .p2align and the
> # leading nop of the inlined call appears to be on the same line
> # as main's call to marker.
> @@ -306,17 +306,17 @@ gdb_test_multiple "bt" $msg {
> }
>
> gdb_test "step" "noinline \\\(\\\) at .*" "enter noinline from outer_inline1"
> -gdb_test "bt" "#0 noinline.*#1 .*outer_inline1.*#2 .*outer_inline2.*#3 main.*" "backtrace at noinline from outer_inline1"
> +gdb_test "bt" "#0 noinline.*#1 .*outer_inline1.*#2 .*outer_inline2.*#3 $hex in main.*" "backtrace at noinline from outer_inline1"
> gdb_test "step" "inlined_fn \\\(\\\) at .*" "enter inlined_fn from noinline"
> -gdb_test "bt" "#0 inlined_fn.*#1 noinline.*#2 .*outer_inline1.*#3 .*outer_inline2.*#4 main.*" "backtrace at inlined_fn from noinline"
> +gdb_test "bt" "#0 inlined_fn.*#1 $hex in noinline.*#2 .*outer_inline1.*#3 .*outer_inline2.*#4 $hex in main.*" "backtrace at inlined_fn from noinline"
> gdb_test "info frame" ".*inlined into frame.*" "inlined_fn from noinline inlined"
> -gdb_test "up" "#1 noinline.*" "up to noinline"
> +gdb_test "up" "#1 $hex in noinline.*" "up to noinline"
> gdb_test "info frame" ".*\n called by frame.*" "noinline from outer_inline1 not inlined"
> gdb_test "up" "#2 .*outer_inline1.*" "up to outer_inline1"
> gdb_test "info frame" ".*inlined into frame.*" "outer_inline1 inlined"
> gdb_test "up" "#3 .*outer_inline2.*" "up to outer_inline2"
> gdb_test "info frame" ".*inlined into frame.*" "outer_inline2 inlined"
> -gdb_test "up" "#4 main.*" "up from outer_inline2"
> +gdb_test "up" "#4 $hex in main.*" "up from outer_inline2"
> gdb_test "info frame" ".*\n caller of frame.*" "main not inlined"
>
> gdb_exit
> diff --git a/gdb/testsuite/gdb.python/py-frame-inline.exp b/gdb/testsuite/gdb.python/py-frame-inline.exp
> index 71bffd375db..aa22001b0d8 100644
> --- a/gdb/testsuite/gdb.python/py-frame-inline.exp
> +++ b/gdb/testsuite/gdb.python/py-frame-inline.exp
> @@ -30,11 +30,11 @@ if ![runto main] then {
> }
>
> gdb_breakpoint [gdb_get_line_number "break-here"]
> -gdb_continue_to_breakpoint "Block break here."
> +gdb_continue_to_breakpoint "continue to 'break here', first time"
>
> gdb_test "info frame" "inlined into frame 1\r\n.*"
>
> -gdb_test "up" "#1 g .*"
> +gdb_test "up" "#1 $hex in g .*"
>
> gdb_test "python print (gdb.selected_frame().read_var('l'))" "\r\n42"
>
> @@ -48,7 +48,7 @@ gdb_test "python print (gdb.selected_frame().read_var('l'))" "\r\n42"
> # the frame cache is flushed somehow after setting the limit, to force
> # frame id recomputation.
> gdb_test_no_output "set backtrace limit 1"
> -gdb_continue_to_breakpoint "Block break here."
> +gdb_continue_to_breakpoint "continue to 'break here', second time"
>
> gdb_test "python print (gdb.newest_frame())" ".*"
>
> --
> 2.14.5
>
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