[PATCH] lto: Set resolution to LDPR_PREVAILING_DEF for non-IR common symbol

From 75c48f7a28f23dcd4a345169a57906dbe39f1431 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <[email protected]>
Date: Thu, 27 Aug 2026 15:49:08 +0800
Subject: [PATCH] lto: Set resolution to LDPR_PREVAILING_DEF for non-IR common
 symbol

Since size or alignment of common symbol may be overridden by another
common symbol, set symbol resolution to LDPR_PREVAILING_DEF, instead of
LDPR_RESOLVED_EXEC, for common symbol in regular object when seeing an
undefined or common symbol from an IR object.

	PR ld/34570
	* plugin.c (get_symbols): Set resolution to LDPR_PREVAILING_DEF
	for common symbol in regular object.
	* testsuite/ld-plugin/pr34570a.c: New file.
	* testsuite/ld-plugin/pr34570a.d: Likewise.
	* testsuite/ld-plugin/pr34570b.c: Likewise.
	* testsuite/ld-plugin/pr34570b.d: Likewise.
	* testsuite/ld-plugin/pr34570c.c: Likewise.
	* testsuite/ld-plugin/pr34570c.d: Likewise.

Signed-off-by: H.J. Lu <[email protected]>
---
 ld/plugin.c                       |  2 +
 ld/testsuite/ld-plugin/lto.exp    | 67 +++++++++++++++++++++++++++++++
 ld/testsuite/ld-plugin/pr34570a.c |  9 +++++
 ld/testsuite/ld-plugin/pr34570a.d |  6 +++
 ld/testsuite/ld-plugin/pr34570b.c |  1 +
 ld/testsuite/ld-plugin/pr34570b.d |  6 +++
 ld/testsuite/ld-plugin/pr34570c.c |  9 +++++
 ld/testsuite/ld-plugin/pr34570c.d |  6 +++
 8 files changed, 106 insertions(+)
 create mode 100644 ld/testsuite/ld-plugin/pr34570a.c
 create mode 100644 ld/testsuite/ld-plugin/pr34570a.d
 create mode 100644 ld/testsuite/ld-plugin/pr34570b.c
 create mode 100644 ld/testsuite/ld-plugin/pr34570b.d
 create mode 100644 ld/testsuite/ld-plugin/pr34570c.c
 create mode 100644 ld/testsuite/ld-plugin/pr34570c.d

diff --git a/ld/plugin.c b/ld/plugin.c
index 1cf5c915b00..5752d647cfe 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -860,6 +860,8 @@ get_symbols (const void *handle, int nsyms, struct ld_plugin_symbol *syms,
 	  else if (owner_sec->owner != NULL
 		   && (owner_sec->owner->flags & DYNAMIC) != 0)
 	    res = LDPR_RESOLVED_DYN;
+	  else if (blhe->type == bfd_link_hash_common)
+	    res = LDPR_PREVAILING_DEF;
 	  else
 	    res = LDPR_RESOLVED_EXEC;
 	}
diff --git a/ld/testsuite/ld-plugin/lto.exp b/ld/testsuite/ld-plugin/lto.exp
index 4504fd4be01..476b605b721 100644
--- a/ld/testsuite/ld-plugin/lto.exp
+++ b/ld/testsuite/ld-plugin/lto.exp
@@ -275,6 +275,73 @@ set lto_link_tests [list \
    {} \
    "libcommon-2.a" \
   ] \
+  [list \
+   "Build pr34570a.exe" \
+   "-flto" \
+   "-flto -fcommon" \
+   {pr34570a.c pr34570b.c} \
+   {{readelf {-s --wide} pr34570a.d}} \
+   "pr34570a.exe" \
+  ] \
+  [list \
+   "Build pr34570b.exe" \
+   "-flto" \
+   "-flto -fcommon" \
+   {pr34570b.c pr34570a.c} \
+   {{readelf {-s --wide} pr34570a.d}} \
+   "pr34570b.exe" \
+  ] \
+  [list \
+   "Build pr34570a.o" \
+   "" \
+   "-O2 -fcommon -flto $lto_no_fat" \
+   {pr34570a.c} \
+   {} \
+   "" \
+   "c" \
+  ] \
+  [list \
+   "Build pr34570b.o" \
+   "" \
+   "-O2 -fcommon -fno-lto" \
+   {pr34570b.c} \
+   {} \
+   "" \
+   "c" \
+  ] \
+  [list \
+   "Build pr34570c.o" \
+   "" \
+   "-O2 -fcommon -flto $lto_no_fat" \
+   {pr34570c.c} \
+   {} \
+   "" \
+   "c" \
+  ] \
+  [list \
+   "Build pr34570c.exe" \
+   "-flto tmpdir/pr34570a.o tmpdir/pr34570b.o" \
+   "" \
+   {dummy.c} \
+   {{readelf {-s --wide} pr34570b.d}} \
+   "pr34570c.exe" \
+  ] \
+  [list \
+   "Build pr34570d.exe" \
+   "-flto tmpdir/pr34570b.o tmpdir/pr34570a.o" \
+   "" \
+   {dummy.c} \
+   {{readelf {-s --wide} pr34570b.d}} \
+   "pr34570d.exe" \
+  ] \
+  [list \
+   "Build pr34570e.exe" \
+   "-flto tmpdir/pr34570c.o tmpdir/pr34570b.o" \
+   "-flto -fcommon" \
+   {dummy.c} \
+   {{readelf {-s --wide} pr34570c.d}} \
+   "pr34570e.exe" \
+  ] \
 ]
 
 if { [at_least_gcc_version 10 0] && [check_lto_shared_available] } {
diff --git a/ld/testsuite/ld-plugin/pr34570a.c b/ld/testsuite/ld-plugin/pr34570a.c
new file mode 100644
index 00000000000..d3ad433e52f
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr34570a.c
@@ -0,0 +1,9 @@
+#include <stdint.h>
+
+char foo[8];
+
+int
+main ()
+{
+  return (uintptr_t) &foo == 0x12345678 ? 0 : 1;
+}
diff --git a/ld/testsuite/ld-plugin/pr34570a.d b/ld/testsuite/ld-plugin/pr34570a.d
new file mode 100644
index 00000000000..6bbc399bf77
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr34570a.d
@@ -0,0 +1,6 @@
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[0-9a-f]+ +8 +OBJECT +LOCAL +DEFAULT .*[0-9]+ _?foo
+#pass
diff --git a/ld/testsuite/ld-plugin/pr34570b.c b/ld/testsuite/ld-plugin/pr34570b.c
new file mode 100644
index 00000000000..e308af97111
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr34570b.c
@@ -0,0 +1 @@
+char foo[1];
diff --git a/ld/testsuite/ld-plugin/pr34570b.d b/ld/testsuite/ld-plugin/pr34570b.d
new file mode 100644
index 00000000000..39d9d7315cb
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr34570b.d
@@ -0,0 +1,6 @@
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[0-9a-f]+ +8 +OBJECT +GLOBAL +DEFAULT .*[0-9]+ _?foo
+#pass
diff --git a/ld/testsuite/ld-plugin/pr34570c.c b/ld/testsuite/ld-plugin/pr34570c.c
new file mode 100644
index 00000000000..ae3ce725e34
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr34570c.c
@@ -0,0 +1,9 @@
+#include <stdint.h>
+
+extern char foo[];
+
+int
+main ()
+{
+  return (uintptr_t) &foo == 0x12345678 ? 0 : 1;
+}
diff --git a/ld/testsuite/ld-plugin/pr34570c.d b/ld/testsuite/ld-plugin/pr34570c.d
new file mode 100644
index 00000000000..c512064fbeb
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr34570c.d
@@ -0,0 +1,6 @@
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[0-9a-f]+ +1 +OBJECT +GLOBAL +DEFAULT .*[0-9]+ _?foo
+#pass
-- 
2.55.0