[PATCH] Fix handling of DW_AT_entry_pc of inlined subroutines

[PATCH] Fix handling of DW_AT_entry_pc of inlined subroutines

[Bernd Edlinger]

It may happen that the inline entry point is not the
start address of the first sub-range of an inline
function.

But the PC for a breakpoint on an inlined subroutine
is always the start address of the first sub-range.

This patch moves the sub-range starting at the entry
point to the first position of the block list.

Therefore the breakpoint on an inlined function
changes in rare cases from the start address of
the first sub-range to the real entry point.

There should always be a subrange that starts at the
entry point, even if that is an empty sub-range.
---
 gdb/dwarf2/read.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 3d0219df054..7a343363c77 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -11285,6 +11285,16 @@ dwarf2_record_block_ranges (struct die_info *die, struct block *block,
       if (die->tag != DW_TAG_compile_unit)
 	ranges_offset += cu->gnu_ranges_base;
 
+      CORE_ADDR entry_pc = (CORE_ADDR) -1;
+      if (die->tag == DW_TAG_inlined_subroutine)
+	{
+	  attr = dwarf2_attr (die, DW_AT_entry_pc, cu);
+	  if (attr != nullptr)
+	    {
+	      entry_pc = per_objfile->relocate (attr->as_address ());
+	    }
+	}
+
       std::vector<blockrange> blockvec;
       dwarf2_ranges_process (ranges_offset, cu, die->tag,
 	[&] (unrelocated_addr start, unrelocated_addr end)
@@ -11294,6 +11304,8 @@ dwarf2_record_block_ranges (struct die_info *die, struct block *block,
 	  cu->get_builder ()->record_block_range (block, abs_start,
 						  abs_end - 1);
 	  blockvec.emplace_back (abs_start, abs_end);
+	  if (entry_pc == abs_start && blockvec.size () > 1)
+	    std::swap (blockvec[0], blockvec[blockvec.size () - 1]);
 	});
 
       block->set_ranges (make_blockranges (objfile, blockvec));
-- 
2.39.2

[PATCH] Fix handling of DW_AT_entry_pc of inlined subroutines

[Bernd Edlinger]

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Hi,


this was previously a part of the "[PATCH v5] Fix range end handling of inlined subroutines"
but this change can be considered to be independent of the range end handling.

It is sometimes the case that the entry_pc points at an empty sub-range, and therefore
this change makes more sense when the range end handling (including empty sub-ranges)
is applied first.

Unfortunately I have no test case for it.

This is similar to the "[PATCHv2] Fix partial symbols"
https://sourceware.org/pipermail/gdb-patches/2020-December/174175.html

Where I have no test case either, nevertheless I am sure it happens.


Thanks
Bernd.


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[-- Attachment #2: 0003-Fix-handling-of-DW_AT_entry_pc-of-inlined-subroutine.patch --]
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From b61ad6070d8ddb13aefaffe56aaf9c09450fb5a0 Mon Sep 17 00:00:00 2001
From: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date: Tue, 3 Nov 2020 18:41:43 +0100
Subject: [PATCH] Fix handling of DW_AT_entry_pc of inlined subroutines

It may happen that the inline entry point is not the
start address of the first sub-range of an inline
function.

But the PC for a breakpoint on an inlined subroutine
is always the start address of the first sub-range.

This patch moves the sub-range starting at the entry
point to the first position of the block list.

Therefore the breakpoint on an inlined function
changes in rare cases from the start address of
the first sub-range to the real entry point.

There should always be a subrange that starts at the
entry point, even if that is an empty sub-range.

2021-01-01  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* dwarf2/read.c (dwarf2_record_block_ranges): Move range beginning
	at DW_AT_entry_pc to the first block range.
---
 gdb/dwarf2/read.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index a48beab..bb050e6 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -14844,6 +14844,18 @@ class process_die_scope
       unsigned long offset = (attr->as_unsigned ()
 			      + (need_ranges_base ? cu->ranges_base : 0));
 
+      CORE_ADDR entry_pc = (CORE_ADDR) -1;
+      if (die->tag == DW_TAG_inlined_subroutine)
+	{
+	  attr = dwarf2_attr (die, DW_AT_entry_pc, cu);
+	  if (attr != nullptr)
+	    {
+	      entry_pc = attr->as_address ();
+	      entry_pc += baseaddr;
+	      entry_pc = gdbarch_adjust_dwarf2_addr (gdbarch, entry_pc);
+	    }
+	}
+
       std::vector<blockrange> blockvec;
       dwarf2_ranges_process (offset, cu, die->tag,
 	[&] (CORE_ADDR start, CORE_ADDR end)
@@ -14854,6 +14866,8 @@ class process_die_scope
 	  end = gdbarch_adjust_dwarf2_addr (gdbarch, end);
 	  cu->get_builder ()->record_block_range (block, start, end - 1);
 	  blockvec.emplace_back (start, end);
+	  if (entry_pc == start && blockvec.size () > 1)
+	    std::swap (blockvec[0], blockvec[blockvec.size () - 1]);
 	});
 
       BLOCK_RANGES(block) = make_blockranges (objfile, blockvec);
-- 
1.9.1