Strip global symbol defined in discarded section

When a global symbol is defined in COMDAT group, we shouldn't leave an
undefined symbol in symbol table when the symbol section is discarded
unless there is a reference to the symbol outside of COMDAT group.

bfd/

	PR ld/17550
	* elf-bfd.h (elf_link_hash_entry): Update comments for indx,
	documenting that indx == -3 if symbol is defined in a discarded
	section.
	* elflink.c (elf_link_add_object_symbols): Set indx to -3 if
	symbol is defined in a discarded section.
	(elf_link_output_extsym): Strip a global symbol defined in a
	discarded section.

ld/

	PR ld/17550
	* testsuite/ld-elf/pr17550-1.s: New file.
	* testsuite/ld-elf/pr17550-2.s: Likewise.
	* testsuite/ld-elf/pr17550-3.s: Likewise.
	* testsuite/ld-elf/pr17550-4.s: Likewise.
	* testsuite/ld-elf/pr17550a.d: Likewise.
	* testsuite/ld-elf/pr17550b.d: Likewise.
	* testsuite/ld-elf/pr17550c.d: Likewise.
	* testsuite/ld-elf/pr17550d.d: Likewise.

8 files changed, 94 insertions, 0 deletions

diff --git a/ld/testsuite/ld-elf/pr17550-1.s b/ld/testsuite/ld-elf/pr17550-1.s
new file mode 100644
index 0000000..3da73dc
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550-1.s
@@ -0,0 +1,9 @@
+	.section .data,"awG",%progbits,foo_group,comdat
+	.dc.a	x_alias
+	.type	x, %object
+	.p2align 2
+	.size	x, 4
+x:
+	.zero	4
+	.globl	x_alias
+	.set	x_alias,x
diff --git a/ld/testsuite/ld-elf/pr17550-2.s b/ld/testsuite/ld-elf/pr17550-2.s
new file mode 100644
index 0000000..eb4120f
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550-2.s
@@ -0,0 +1,6 @@
+	.section .data,"awG",%progbits,foo_group,comdat
+	.type	x, %object
+	.p2align 2
+	.size	x, 4
+x:
+	.zero	4
diff --git a/ld/testsuite/ld-elf/pr17550-3.s b/ld/testsuite/ld-elf/pr17550-3.s
new file mode 100644
index 0000000..3d7c252
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550-3.s
@@ -0,0 +1,14 @@
+	.data
+	.dc.a	y
+	.section .data,"awG",%progbits,foo_group,comdat
+	.type	y, %object
+	.size	y, 4
+y:
+	.zero	4
+	.globl	x
+	.type	x, %object
+	.size	x, 4
+x:
+	.zero	4
+	.globl	x_alias
+	.set	x_alias,x
diff --git a/ld/testsuite/ld-elf/pr17550-4.s b/ld/testsuite/ld-elf/pr17550-4.s
new file mode 100644
index 0000000..d0442fd
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550-4.s
@@ -0,0 +1,15 @@
+	.data
+	.dc.a	y
+	.section .data,"awG",%progbits,foo_group,comdat
+	.globl	y
+	.type	y, %object
+	.size	y, 4
+y:
+	.zero	4
+	.globl	x
+	.type	x, %object
+	.size	x, 4
+x:
+	.zero	4
+	.globl	x_alias
+	.set	x_alias,x
diff --git a/ld/testsuite/ld-elf/pr17550a.d b/ld/testsuite/ld-elf/pr17550a.d
new file mode 100644
index 0000000..c8f0424
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550a.d
@@ -0,0 +1,14 @@
+#source: pr17550-1.s
+#source: pr17550-2.s
+#ld: -r
+#readelf: -s --wide
+#notarget: alpha-*-* cr16-*-* crx-*-* d30v-*-* dlx-*-* i960-*-* pj*-*-*
+# Disabled on alpha because alpha has a different .set directive.
+# cr16 and crx use non-standard scripts with memory regions, which don't
+# play well with comdat group sections under ld -r.  Generic linker
+# targets don't support comdat group sections.
+
+#failif
+#...
+ +[0-9]+: +[0-9a-f]+ +0 +OBJECT +GLOBAL +DEFAULT +UND x_alias
+#...
diff --git a/ld/testsuite/ld-elf/pr17550b.d b/ld/testsuite/ld-elf/pr17550b.d
new file mode 100644
index 0000000..d189747
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550b.d
@@ -0,0 +1,14 @@
+#source: pr17550-2.s
+#source: pr17550-1.s
+#ld: -r
+#readelf: -s --wide
+#notarget: alpha-*-* cr16-*-* crx-*-* d30v-*-* dlx-*-* i960-*-* pj*-*-*
+# Disabled on alpha because alpha has a different .set directive.
+# cr16 and crx use non-standard scripts with memory regions, which don't
+# play well with comdat group sections under ld -r.  Generic linker
+# targets don't support comdat group sections.
+
+#failif
+#...
+ +[0-9]+: +[0-9a-f]+ +0 +OBJECT +GLOBAL +DEFAULT +UND x_alias
+#...
diff --git a/ld/testsuite/ld-elf/pr17550c.d b/ld/testsuite/ld-elf/pr17550c.d
new file mode 100644
index 0000000..23a83f1
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550c.d
@@ -0,0 +1,9 @@
+#source: pr17550-2.s
+#source: pr17550-3.s
+#ld: -r
+#error: .*: defined in discarded section `\.data\[foo_group\]'
+#notarget: alpha-*-* cr16-*-* crx-*-* d30v-*-* dlx-*-* i960-*-* pj*-*-*
+# Disabled on alpha because alpha has a different .set directive.
+# cr16 and crx use non-standard scripts with memory regions, which don't
+# play well with comdat group sections under ld -r.  Generic linker
+# targets don't support comdat group sections.
diff --git a/ld/testsuite/ld-elf/pr17550d.d b/ld/testsuite/ld-elf/pr17550d.d
new file mode 100644
index 0000000..e8fad96
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr17550d.d
@@ -0,0 +1,13 @@
+#source: pr17550-2.s
+#source: pr17550-4.s
+#ld: -r
+#readelf: -s --wide
+#notarget: alpha-*-* cr16-*-* crx-*-* d30v-*-* dlx-*-* i960-*-* pj*-*-*
+# Disabled on alpha because alpha has a different .set directive.
+# cr16 and crx use non-standard scripts with memory regions, which don't
+# play well with comdat group sections under ld -r.  Generic linker
+# targets don't support comdat group sections.
+
+#...
+ +[0-9]+: +[0-9a-f]+ +0 +OBJECT +GLOBAL +DEFAULT +UND y
+#pass