[gdb/symtab] Prefer def over decl (inter-CU case, with context)

Message ID 20200409210804.GA6512@delia
State New
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Series
  • [gdb/symtab] Prefer def over decl (inter-CU case, with context)
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Commit Message

Tom de Vries April 9, 2020, 9:08 p.m.
Hi,

This is a follow-up patch on "[PATCH][gdb/symtab] Prefer def over decl
(inter-CU case)" (
https://sourceware.org/pipermail/gdb-patches/2020-April/167489.html ).

Consider the test-case from that patch.  It contains a decl and def of var a
in different CUs, and tests whether var a can be printed using the def, even
if the decl is found first.

However, the test-case does this in a contextless environment, so if we add to
the test-case like this to set the context to the CU containing main:
...
 gdb_test "p a" { = \{1, 2\}}
+
+if ![runto_main] then {
+    fail "can't run to main"
+    return 0
+}
+
+gdb_test "p a" { = \{1, 2\}}
...
then the second test fails, because the decl is found in the context.

Fix this by preferring defs over decls in lookup_global_symbol.

Build and reg-tested on x86_64-linux.

OK for trunk?

Thanks,
- Tom

[gdb/symtab] Prefer def over decl (inter-CU case, with context)

gdb/ChangeLog:

2020-04-09  Tom de Vries  <tdevries@suse.de>

	* symtab.c (lookup_global_symbol): Prefer def over decl.

gdb/testsuite/ChangeLog:

2020-04-09  Tom de Vries  <tdevries@suse.de>

	* gdb.base/decl-before-def.exp: Run to main and print a again.

---
 gdb/symtab.c                               | 16 +++++++++++-----
 gdb/testsuite/gdb.base/decl-before-def.exp |  7 +++++++
 2 files changed, 18 insertions(+), 5 deletions(-)

Comments

Tom de Vries April 23, 2020, 1:57 p.m. | #1
On 09-04-2020 23:08, Tom de Vries wrote:
> Hi,

> 

> This is a follow-up patch on "[PATCH][gdb/symtab] Prefer def over decl

> (inter-CU case)" (

> https://sourceware.org/pipermail/gdb-patches/2020-April/167489.html ).

> 

> Consider the test-case from that patch.  It contains a decl and def of var a

> in different CUs, and tests whether var a can be printed using the def, even

> if the decl is found first.

> 

> However, the test-case does this in a contextless environment, so if we add to

> the test-case like this to set the context to the CU containing main:

> ...

>  gdb_test "p a" { = \{1, 2\}}

> +

> +if ![runto_main] then {

> +    fail "can't run to main"

> +    return 0

> +}

> +

> +gdb_test "p a" { = \{1, 2\}}

> ...

> then the second test fails, because the decl is found in the context.

> 

> Fix this by preferring defs over decls in lookup_global_symbol.

> 

> Build and reg-tested on x86_64-linux.

> 


Committed.

Thanks,
- Tom

Patch

diff --git a/gdb/symtab.c b/gdb/symtab.c
index e063af80fe..6ae69f2e25 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -2718,17 +2718,23 @@  lookup_global_symbol (const char *name,
      global block first.  This yields "more expected" behavior, and is
      needed to support 'FILENAME'::VARIABLE lookups.  */
   const struct block *global_block = block_global_block (block);
+  symbol *sym = NULL;
   if (global_block != nullptr)
     {
-      symbol *sym = lookup_symbol_in_block (name,
-					    symbol_name_match_type::FULL,
-					    global_block, domain);
-      if (sym != nullptr)
+      sym = lookup_symbol_in_block (name,
+				    symbol_name_match_type::FULL,
+				    global_block, domain);
+      if (sym != NULL && best_symbol (sym, domain))
 	return { sym, global_block };
     }
 
   struct objfile *objfile = lookup_objfile_from_block (block);
-  return lookup_global_or_static_symbol (name, GLOBAL_BLOCK, objfile, domain);
+  block_symbol bs
+    = lookup_global_or_static_symbol (name, GLOBAL_BLOCK, objfile, domain);
+  if (better_symbol (sym, bs.symbol, domain) == sym)
+    return { sym, global_block };
+  else
+    return bs;
 }
 
 bool
diff --git a/gdb/testsuite/gdb.base/decl-before-def.exp b/gdb/testsuite/gdb.base/decl-before-def.exp
index feb2084a82..0af3bdf3c7 100644
--- a/gdb/testsuite/gdb.base/decl-before-def.exp
+++ b/gdb/testsuite/gdb.base/decl-before-def.exp
@@ -24,3 +24,10 @@  if {[prepare_for_testing "failed to prepare" $testfile $sources]} {
 gdb_test "maint expand-symtabs"
 
 gdb_test "p a" { = \{1, 2\}}
+
+if ![runto_main] then {
+    fail "can't run to main"
+    return 0
+}
+
+gdb_test "p a" { = \{1, 2\}}