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

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

[Tom de Vries]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=70bc38f51381698804566504e25d197e8e731d2d

commit 70bc38f51381698804566504e25d197e8e731d2d
Author: Tom de Vries <tdevries@suse.de>
Date:   Thu Apr 23 15:42:47 2020 +0200

    [gdb/symtab] Prefer def over decl (inter-CU case, with context)
    
    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.
    
    gdb/ChangeLog:
    
    2020-04-23  Tom de Vries  <tdevries@suse.de>
    
            * symtab.c (lookup_global_symbol): Prefer def over decl.
    
    gdb/testsuite/ChangeLog:
    
    2020-04-23  Tom de Vries  <tdevries@suse.de>
    
            * gdb.base/decl-before-def.exp: Run to main and print a again.

Diff:
---
 gdb/ChangeLog                              |  4 ++++
 gdb/symtab.c                               | 16 +++++++++++-----
 gdb/testsuite/ChangeLog                    |  4 ++++
 gdb/testsuite/gdb.base/decl-before-def.exp |  7 +++++++
 4 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f1ebf09ff46..109456689aa 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2020-04-23  Tom de Vries  <tdevries@suse.de>
+
+	* symtab.c (lookup_global_symbol): Prefer def over decl.
+
 2020-04-23  Tom de Vries  <tdevries@suse.de>
 
 	PR symtab/25807
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 1eef97837e8..4e9f91056b8 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/ChangeLog b/gdb/testsuite/ChangeLog
index e37aca2b5af..10683db566d 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2020-04-23  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.base/decl-before-def.exp: Run to main and print a again.
+
 2020-04-23  Tom de Vries  <tdevries@suse.de>
 
 	* gdb.base/decl-before-def-decl.c: New test.
diff --git a/gdb/testsuite/gdb.base/decl-before-def.exp b/gdb/testsuite/gdb.base/decl-before-def.exp
index feb2084a82f..0af3bdf3c75 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\}}