[PATCH 2/2] Free multidicts from blockvector

Tom Tromey
2025-10-23T17:21:17Z

Currently, nothing in the tree ever calls mdict_free. However, code
does heap-allocate some multidicts. A simple way to see this is to
use valgrind, run "gdb -readnow" on the executable created by
gdb.dwarf2/struct-with-sig.exp, and then use "file" to clear the
objfile list. This yields:

==1522843== 144 (16 direct, 128 indirect) bytes in 1 blocks are definitely lost in loss record 905 of 3,005
==1522843== at 0x4843866: malloc (vg_replace_malloc.c:446)
==1522843== by 0x48E397: xmalloc (alloc.c:52)
==1522843== by 0x59DE66: multidictionary* xnew<multidictionary>() (poison.h:102)
==1522843== by 0x59CFF4: mdict_create_hashed_expandable(language) (dictionary.c:965)
==1522843== by 0x50A269: buildsym_compunit::finish_block_internal(symbol*, pending**, pending_block*, dynamic_prop const*, unsigned long, unsigned long, int, int) (buildsym.c:221)
==1522843== by 0x50AE04: buildsym_compunit::end_compunit_symtab_get_static_block(unsigned long, int, int) (buildsym.c:818)
==1522843== by 0x50C4CF: buildsym_compunit::end_expandable_symtab(unsigned long) (buildsym.c:1037)
==1522843== by 0x61DBC6: process_full_type_unit (read.c:4970)

This patch fixes the leaks by calling mdict_free when a blockvector is
destroyed.
---
gdb/block.c | 6 ++++++
gdb/block.h | 2 ++
2 files changed, 8 insertions(+)

diff --git a/gdb/block.c b/gdb/block.c
index 02e6d0e4be2bab2c1b3750a2f396e4bc97b7bc5d..2d8d40ec4eb94a1c891a3f8b48972eff3050e66d 100644
--- a/gdb/block.c
+++ b/gdb/block.c
@@ -842,6 +842,12 @@ blockvector::append_block (struct block *block)
m_blocks.push_back (block);
}

+blockvector::~blockvector ()
+{
+ for (struct block *bl : m_blocks)
+ mdict_free (bl->multidict ());
+}
+
/* Implement 'maint info blocks' command. If passed an argument then
print a list of all blocks at the given address. With no arguments
then list all blocks at the current address of the current inferior. */
diff --git a/gdb/block.h b/gdb/block.h
index 61070619ca7daa7b3310a9c5cd8d6ca86c044ada..98ce5a3839dbb8419c9e3a918d27b3b58485fea4 100644
--- a/gdb/block.h
+++ b/gdb/block.h
@@ -424,6 +424,8 @@ struct blockvector
: m_blocks (nblocks, nullptr)
{}

+ ~blockvector ();
+
/* Return a view on the blocks of this blockvector. */
gdb::array_view<struct block *> blocks ()
{

--
2.49.0