section_table_xfer_memory: Replace section name with callback predicate

This patch is motivated by the need to be able to select sections
that section_table_xfer_memory_partial should consider for memory
transfers.  I'll use this facility in the next patch in this series.

section_table_xfer_memory_partial() can currently be passed a section
name which may be used to make name-based selections.  This is similar
to what I want to do, except that I want to be able to consider
section flags instead of the name.

I'm replacing the section name parameter with a predicate that,
when passed a pointer to a target_section struct, will return
true if that section should be further considered, or false which
indicates that it shouldn't.

I've converted the one existing use where a non-NULL section
name is passed to section_table_xfer_memory_partial().   Instead
of passing the section name, it now looks like this:

	  auto match_cb = [=] (const struct target_section *s)
	    {
	      return (strcmp (section_name, s->the_bfd_section->name) == 0);
	    };

	  return section_table_xfer_memory_partial (readbuf, writebuf,
						    memaddr, len, xfered_len,
						    table->sections,
						    table->sections_end,
						    match_cb);

The other callers all passed NULL; they've been simplified somewhat
in that they no longer need to pass NULL.

gdb/ChangeLog:

	* exec.h (section_table_xfer_memory): Revise declaration,
	replacing section name parameter with an optional callback
	predicate.
	* exec.c (section_table_xfer_memory): Likewise.
	* bfd-target.c, exec.c, target.c, corelow.c: Adjust all callers
	of section_table_xfer_memory.

1 files changed, 10 insertions, 3 deletions

diff --git a/gdb/exec.h b/gdb/exec.h
index 54e6ff4..82eb39c 100644
--- a/gdb/exec.h
+++ b/gdb/exec.h
@@ -65,8 +65,13 @@ extern enum target_xfer_status
    Request to transfer up to LEN 8-bit bytes of the target sections
    defined by SECTIONS and SECTIONS_END.  The OFFSET specifies the
    starting address.
-   If SECTION_NAME is not NULL, only access sections with that same
-   name.
+
+   The MATCH_CB predicate is optional; when provided it will be called
+   for each section under consideration.  When MATCH_CB evaluates as
+   true, the section remains under consideration; a false result
+   removes it from consideration for performing the memory transfers
+   noted above.  See memory_xfer_partial_1() in target.c for an
+   example.
 
    Return the number of bytes actually transfered, or zero when no
    data is available for the requested range.
@@ -83,7 +88,9 @@ extern enum target_xfer_status
 				     ULONGEST, ULONGEST, ULONGEST *,
 				     struct target_section *,
 				     struct target_section *,
-				     const char *);
+				     gdb::function_view<bool
+				       (const struct target_section *)> match_cb
+				         = nullptr);
 
 /* Read from mappable read-only sections of BFD executable files.
    Similar to exec_read_partial_read_only, but return