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[review v3] Don't make an extra copy + allocation of the demangled name
- From: "Christian Biesinger (Code Review)" <gerrit at gnutoolchain-gerrit dot osci dot io>
- To: Christian Biesinger <cbiesinger at google dot com>, Luis Machado <luis dot machado at linaro dot org>, Tom Tromey <tromey at sourceware dot org>, Simon Marchi <simon dot marchi at polymtl dot ca>, gdb-patches at sourceware dot org
- Date: Wed, 23 Oct 2019 12:51:18 -0400
- Subject: [review v3] Don't make an extra copy + allocation of the demangled name
- Auto-submitted: auto-generated
- References: <gerrit.1571352433000.Ie6ad50e1e1e73509f55d756f0a437897bb93e3b0@gnutoolchain-gerrit.osci.io>
- Reply-to: cbiesinger at google dot com, simon dot marchi at polymtl dot ca, tromey at sourceware dot org, luis dot machado at linaro dot org, cbiesinger at google dot com, gdb-patches at sourceware dot org
Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/132
......................................................................
Don't make an extra copy + allocation of the demangled name
We can just keep around the malloc()-ed name we got from bfd and free
it later.
gdb/ChangeLog:
2019-10-02 Christian Biesinger <cbiesinger@google.com>
* symtab.c (struct demangled_name_entry): Change demangled name
to a unique_xmalloc_ptr<char>, now that we don't allocate it as
part of the struct anymore.
(symbol_set_names): No longer obstack allocate + copy the demangled
name, just store the allocated name from bfd.
Change-Id: Ie6ad50e1e1e73509f55d756f0a437897bb93e3b0
---
M gdb/symtab.c
1 file changed, 13 insertions(+), 25 deletions(-)
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 160a4c0..8553fc9 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -723,7 +723,7 @@
gdb::string_view mangled;
enum language language;
- char demangled[1];
+ gdb::unique_xmalloc_ptr<char> demangled;
};
/* Hash function for the demangled name hash. */
@@ -880,64 +880,52 @@
if (*slot == NULL
/* A C version of the symbol may have already snuck into the table.
This happens to, e.g., main.init (__go_init_main). Cope. */
- || (gsymbol->language == language_go
- && (*slot)->demangled[0] == '\0'))
+ || (gsymbol->language == language_go && (*slot)->demangled == nullptr))
{
- char *demangled_name_ptr
- = symbol_find_demangled_name (gsymbol, linkage_name_copy);
- gdb::unique_xmalloc_ptr<char> demangled_name (demangled_name_ptr);
- int demangled_len = demangled_name ? strlen (demangled_name.get ()) : 0;
+ gdb::unique_xmalloc_ptr<char> demangled_name_ptr
+ (symbol_find_demangled_name (gsymbol, linkage_name_copy));
/* Suppose we have demangled_name==NULL, copy_name==0, and
linkage_name_copy==linkage_name. In this case, we already have the
mangled name saved, and we don't have a demangled name. So,
you might think we could save a little space by not recording
this in the hash table at all.
-
+
It turns out that it is actually important to still save such
an entry in the hash table, because storing this name gives
us better bcache hit rates for partial symbols. */
- if (!copy_name && linkage_name_copy == linkage_name)
+ if (!copy_name)
{
*slot
= ((struct demangled_name_entry *)
obstack_alloc (&per_bfd->storage_obstack,
- offsetof (struct demangled_name_entry, demangled)
- + demangled_len + 1));
+ sizeof (demangled_name_entry)));
new (*slot) demangled_name_entry
(gdb::string_view (linkage_name, len));
}
else
{
- char *mangled_ptr;
-
/* If we must copy the mangled name, put it directly after
- the demangled name so we can have a single
- allocation. */
+ the struct so we can have a single allocation. */
*slot
= ((struct demangled_name_entry *)
obstack_alloc (&per_bfd->storage_obstack,
- offsetof (struct demangled_name_entry, demangled)
- + len + demangled_len + 2));
- mangled_ptr = &((*slot)->demangled[demangled_len + 1]);
+ sizeof (demangled_name_entry) + len + 1));
+ char *mangled_ptr = reinterpret_cast<char*> (*slot + 1);
strcpy (mangled_ptr, linkage_name_copy);
new (*slot) demangled_name_entry
(gdb::string_view (mangled_ptr, len));
}
+ (*slot)->demangled = std::move (demangled_name_ptr);
(*slot)->language = gsymbol->language;
-
- if (demangled_name != NULL)
- strcpy ((*slot)->demangled, demangled_name.get ());
- else
- (*slot)->demangled[0] = '\0';
}
else if (gsymbol->language == language_unknown
|| gsymbol->language == language_auto)
gsymbol->language = (*slot)->language;
gsymbol->name = (*slot)->mangled.data ();
- if ((*slot)->demangled[0] != '\0')
- symbol_set_demangled_name (gsymbol, (*slot)->demangled,
+ if ((*slot)->demangled != nullptr)
+ symbol_set_demangled_name (gsymbol, (*slot)->demangled.get (),
&per_bfd->storage_obstack);
else
symbol_set_demangled_name (gsymbol, NULL, &per_bfd->storage_obstack);