[Bug libbacktrace/89273] New: Count inlined functions in skip parm for backtrace_full and backtrace_print

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89273

            Bug ID: 89273
           Summary: Count inlined functions in skip parm for
                    backtrace_full and backtrace_print
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: libbacktrace
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
                CC: ian at gcc dot gnu.org
  Target Milestone: ---

[ Proposed here: https://gcc.gnu.org/ml/gcc-patches/2019-02/msg00579.html ]

The btest test-case modified like this:
...
diff --git a/libbacktrace/btest.c b/libbacktrace/btest.c
index b1c2a2a860d..0925882aed1 100644
--- a/libbacktrace/btest.c
+++ b/libbacktrace/btest.c
@@ -140,7 +140,7 @@ f13 (int f1line, int f2line)
   data.failed = 0;

   f3line = __LINE__ + 1;
-  i = backtrace_full (state, 0, callback_one, error_callback_one, &data);
+  i = backtrace_full (state, 1, callback_one, error_callback_one, &data);

   if (i != 0)
     {
@@ -148,9 +148,9 @@ f13 (int f1line, int f2line)
       data.failed = 1;
     }

-  check ("test2", 0, all, f3line, "f13", "btest.c", &data.failed);
-  check ("test2", 1, all, f2line, "f12", "btest.c", &data.failed);
-  check ("test2", 2, all, f1line, "test2", "btest.c", &data.failed);
+  //check ("test2", 0, all, f3line, "f13", "btest.c", &data.failed);
+  check ("test2", 0, all, f2line, "f12", "btest.c", &data.failed);
+  check ("test2", 1, all, f1line, "test2", "btest.c", &data.failed);

   printf ("%s: backtrace_full inline\n", data.failed ? "FAIL" : "PASS");

...

fails like this:
...
PASS: backtrace_full noinline
test2: [0]: got ../csu/libc-start.c expected btest.c
test2: [0]: got 308 expected 126
test2: [0]: got __libc_start_main expected f12
FAIL: backtrace_full inline
PASS: backtrace_simple noinline
PASS: backtrace_simple inline
PASS: backtrace_syminfo variable
...

This is expected behaviour: "SKIP is the number of frames to skip", so the
inline functions don't count.

But arguably, it would be more intuitive if the skip parameter matched the
reduction in number of callbacks in backtrace_full.