[2/2] Specialize partial_symtab for DWARF include files
Commit Message
Include files are represented by a partial symtab, but don't expand to
anything. From dwarf2_psymtab::expand_psymtab:
if (per_cu == NULL)
{
/* It's an include file, no symbols to read for it.
Everything is in the parent symtab. */
readin = true;
return;
}
This patch introduces a new specialization of partial_symtab to handle
this case. In addition to being slightly smaller, I believe an
include file is the only situation where a DWARF psymtab can result in
a null compunit_symtab. This adds an assert to that effect as well.
This change will simplify one of the psymtab sharing patches.
gdb/ChangeLog
2020-02-25 Tom Tromey <tom@tromey.com>
* dwarf2/read.c (struct dwarf2_include_psymtab): New.
(dwarf2_create_include_psymtab): Use dwarf2_include_psymtab.
(dwarf2_psymtab::expand_psymtab, dwarf2_psymtab::readin_p)
(dwarf2_psymtab::get_compunit_symtab): Remove null checks for
per_cu_data.
---
gdb/ChangeLog | 8 +++++++
gdb/dwarf2/read.c | 61 ++++++++++++++++++++++++++++++++---------------
2 files changed, 50 insertions(+), 19 deletions(-)
Comments
On 2020-02-25 8:09 a.m., Tom Tromey wrote:
> Include files are represented by a partial symtab, but don't expand to
> anything. From dwarf2_psymtab::expand_psymtab:
>
> if (per_cu == NULL)
> {
> /* It's an include file, no symbols to read for it.
> Everything is in the parent symtab. */
> readin = true;
> return;
> }
>
> This patch introduces a new specialization of partial_symtab to handle
> this case. In addition to being slightly smaller, I believe an
> include file is the only situation where a DWARF psymtab can result in
> a null compunit_symtab. This adds an assert to that effect as well.
> This change will simplify one of the psymtab sharing patches.
>
> gdb/ChangeLog
> 2020-02-25 Tom Tromey <tom@tromey.com>
>
> * dwarf2/read.c (struct dwarf2_include_psymtab): New.
> (dwarf2_create_include_psymtab): Use dwarf2_include_psymtab.
> (dwarf2_psymtab::expand_psymtab, dwarf2_psymtab::readin_p)
> (dwarf2_psymtab::get_compunit_symtab): Remove null checks for
> per_cu_data.
Hi Tom,
From what I understand, this is fine, thanks.
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index 8c40ddb727a..d22a53deb25 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -5894,6 +5894,45 @@ read_abbrev_offset (struct dwarf2_per_objfile *dwarf2_per_objfile,
> return (sect_offset) read_offset (abfd, info_ptr, offset_size);
> }
>
> +/* A partial symtab that is used only for include files. */
> +struct dwarf2_include_psymtab : public partial_symtab
> +{
> + dwarf2_include_psymtab (const char *filename, struct objfile *objfile)
> + : partial_symtab (filename, objfile)
> + {
> + }
> +
> + void read_symtab (struct objfile *objfile) override
> + {
> + expand_psymtab (objfile);
> + }
> +
> + void expand_psymtab (struct objfile *objfile) override
> + {
> + if (m_readin)
> + return;
> + /* It's an include file, no symbols to read for it.
> + Everything is in the parent symtab. */
> + read_dependencies (objfile);
> + m_readin = true;
> + }
> +
> + bool readin_p () const override
> + {
> + return m_readin;
> + }
> +
> + struct compunit_symtab *get_compunit_symtab () const
> + override
The override can be on the previous line.
Simon
>> + struct compunit_symtab *get_compunit_symtab () const
>> + override
Simon> The override can be on the previous line.
Thanks. I checked it in with that change.
Tom
@@ -5894,6 +5894,45 @@ read_abbrev_offset (struct dwarf2_per_objfile *dwarf2_per_objfile,
return (sect_offset) read_offset (abfd, info_ptr, offset_size);
}
+/* A partial symtab that is used only for include files. */
+struct dwarf2_include_psymtab : public partial_symtab
+{
+ dwarf2_include_psymtab (const char *filename, struct objfile *objfile)
+ : partial_symtab (filename, objfile)
+ {
+ }
+
+ void read_symtab (struct objfile *objfile) override
+ {
+ expand_psymtab (objfile);
+ }
+
+ void expand_psymtab (struct objfile *objfile) override
+ {
+ if (m_readin)
+ return;
+ /* It's an include file, no symbols to read for it.
+ Everything is in the parent symtab. */
+ read_dependencies (objfile);
+ m_readin = true;
+ }
+
+ bool readin_p () const override
+ {
+ return m_readin;
+ }
+
+ struct compunit_symtab *get_compunit_symtab () const
+ override
+ {
+ return nullptr;
+ }
+
+private:
+
+ bool m_readin = false;
+};
+
/* Allocate a new partial symtab for file named NAME and mark this new
partial symtab as being an include of PST. */
@@ -5901,7 +5940,7 @@ static void
dwarf2_create_include_psymtab (const char *name, dwarf2_psymtab *pst,
struct objfile *objfile)
{
- dwarf2_psymtab *subpst = new dwarf2_psymtab (name, objfile);
+ dwarf2_include_psymtab *subpst = new dwarf2_include_psymtab (name, objfile);
if (!IS_ABSOLUTE_PATH (subpst->filename))
{
@@ -5912,11 +5951,6 @@ dwarf2_create_include_psymtab (const char *name, dwarf2_psymtab *pst,
subpst->dependencies = objfile->partial_symtabs->allocate_dependencies (1);
subpst->dependencies[0] = pst;
subpst->number_of_dependencies = 1;
-
- /* No private part is necessary for include psymtabs. This property
- can be used to differentiate between such include psymtabs and
- the regular ones. */
- subpst->per_cu_data = nullptr;
}
/* Read the Line Number Program data and extract the list of files
@@ -8827,24 +8861,13 @@ process_queue (struct dwarf2_per_objfile *dwarf2_per_objfile)
void
dwarf2_psymtab::expand_psymtab (struct objfile *objfile)
{
- struct dwarf2_per_cu_data *per_cu;
-
if (readin)
return;
read_dependencies (objfile);
- per_cu = per_cu_data;
-
- if (per_cu == NULL)
- {
- /* It's an include file, no symbols to read for it.
- Everything is in the parent symtab. */
- readin = true;
- return;
- }
-
- dw2_do_instantiate_symtab (per_cu, false);
+ dw2_do_instantiate_symtab (per_cu_data, false);
+ gdb_assert (get_compunit_symtab () != nullptr);
}
/* Trivial hash function for die_info: the hash value of a DIE