elf: Strip unreferenced weak undefined symbols

Linker will resolve an undefined symbol only if it is referenced by
relocation.  Unreferenced weak undefined symbols serve no purpose.
Weak undefined symbols appear in the dynamic symbol table only when they
are referenced by dynamic relocation.  Mark symbols with relocation and
strip undefined weak symbols if they don't have relocation and aren't
in the dynamic symbol table.

bfd/

	PR ld/31652
	* elf-bfd.h (elf_link_hash_entry): Add has_reloc.
	* elf-vxworks.c (elf_vxworks_emit_relocs): Set has_reloc.
	* elflink.c (_bfd_elf_link_output_relocs): Likewise.
	(elf_link_output_extsym): Strip undefined weak symbols if they
	don't have relocation and aren't in the dynamic symbol table.

ld/

	PR ld/31652
	* testsuite/ld-elf/elf.exp: Run undefweak tests.
	* testsuite/ld-elf/undefweak-1.rd: New file.
	* testsuite/ld-elf/undefweak-1a.s: Likewise.
	* testsuite/ld-elf/undefweak-1b.s: Likewise.
	* testsuite/ld-x86-64/weakundef-1.nd: Likewise.
	* testsuite/ld-x86-64/weakundef-1a.s: Likewise.
	* testsuite/ld-x86-64/weakundef-1b.s: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run undefweak tests.

8 files changed, 87 insertions, 0 deletions

diff --git a/ld/testsuite/ld-elf/elf.exp b/ld/testsuite/ld-elf/elf.exp
index 685b875..874ba66 100644
--- a/ld/testsuite/ld-elf/elf.exp
+++ b/ld/testsuite/ld-elf/elf.exp
@@ -171,6 +171,21 @@ run_ld_link_tests [list \
 	"implib" ] \
 ] \[uses_genelf\]
 
+run_ld_link_tests [list \
+    [list "Generate undefweak-1.a" \
+	"" "" \
+	$hpux \
+	{undefweak-1a.s} \
+	{} \
+	"undefweak-1.a" ] \
+    [list "Generate undefweak-1.o" \
+	"-r" "tmpdir/undefweak-1.a" \
+	$hpux \
+	{undefweak-1b.s} \
+	{{readelf {-rsW} undefweak-1.rd}} \
+	"undefweak-1.o" ] \
+] \[uses_genelf\]
+
 #v850 gas complains about .tbss.var section attributes.
 if { [check_gc_sections_available] && ![istarget "v850-*-*"] } {
     run_ld_link_tests {
diff --git a/ld/testsuite/ld-elf/undefweak-1.rd b/ld/testsuite/ld-elf/undefweak-1.rd
new file mode 100644
index 0000000..5b48c13
--- /dev/null
+++ b/ld/testsuite/ld-elf/undefweak-1.rd
@@ -0,0 +1,10 @@
+#source: undefweak-1a.s
+#source: undefweak-1b.s
+#as:
+#ld: -r
+#readelf: -sW
+
+#failif
+#...
+.*: 0+ +0 +FUNC +WEAK +DEFAULT +UND +bar
+#pass
diff --git a/ld/testsuite/ld-elf/undefweak-1a.s b/ld/testsuite/ld-elf/undefweak-1a.s
new file mode 100644
index 0000000..1d885fb
--- /dev/null
+++ b/ld/testsuite/ld-elf/undefweak-1a.s
@@ -0,0 +1,14 @@
+	.section .text.foobar,"axG",%progbits,foo,comdat
+	.weak foo
+	.type foo,%function
+foo:
+	.nop
+	.size foo, . - foo
+	.weak bar
+	.set bar, foo
+	.text
+	.global baz
+	.type baz,%function
+baz:
+	.dc.a foo
+	.size baz, . - baz
diff --git a/ld/testsuite/ld-elf/undefweak-1b.s b/ld/testsuite/ld-elf/undefweak-1b.s
new file mode 100644
index 0000000..8ba34ea
--- /dev/null
+++ b/ld/testsuite/ld-elf/undefweak-1b.s
@@ -0,0 +1,10 @@
+	.section .text.foobar,"axG",%progbits,foo,comdat
+	.weak foo
+	.type foo,%function
+foo:
+	.nop
+	.size foo, . - foo
+	.text
+	.global _start
+	.set _start,foo
+	.dc.a baz
diff --git a/ld/testsuite/ld-x86-64/weakundef-1.nd b/ld/testsuite/ld-x86-64/weakundef-1.nd
new file mode 100644
index 0000000..c4c89bf
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/weakundef-1.nd
@@ -0,0 +1,6 @@
+#nm: -n
+#target: x86_64-*-*
+
+#...
+ +w +bar
+#pass
diff --git a/ld/testsuite/ld-x86-64/weakundef-1a.s b/ld/testsuite/ld-x86-64/weakundef-1a.s
new file mode 100644
index 0000000..b6eea32
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/weakundef-1a.s
@@ -0,0 +1,6 @@
+	.text
+	.global foo
+	.type foo,%function
+foo:
+	.nop
+	.size foo, . - foo
diff --git a/ld/testsuite/ld-x86-64/weakundef-1b.s b/ld/testsuite/ld-x86-64/weakundef-1b.s
new file mode 100644
index 0000000..3d2da7d
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/weakundef-1b.s
@@ -0,0 +1,8 @@
+	.weak bar
+	.text
+	.global _start
+	.type _start,%function
+_start:
+	mov	bar@GOTPCREL(%rip), %rax
+	mov	foo@GOTPCREL(%rip), %rax
+	.size _start, . - _start
diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp
index e370f39..6546fff 100644
--- a/ld/testsuite/ld-x86-64/x86-64.exp
+++ b/ld/testsuite/ld-x86-64/x86-64.exp
@@ -264,6 +264,24 @@ run_ld_link_tests [list \
 	 {objdump -drj.plt tlsdesc.pd}} \
 	 "libtlsdesc.so" \
     ] \
+    [list \
+	"Generate x86-64-weakundef-1.so" \
+	"-shared -melf_x86_64" \
+	"" \
+	"--64" \
+	{weakundef-1a.s} \
+	{} \
+	"x86-64-weakundef-1.so" \
+    ] \
+    [list \
+	"Generate x86-64-weakundef-1" \
+	"-melf_x86_64" \
+	"tmpdir/x86-64-weakundef-1.so" \
+	"--64" \
+	{weakundef-1b.s} \
+	{{nm -n weakundef-1.nd}} \
+	"x86-64-weakundef-1" \
+    ] \
 ]
 
 set test_name "Mixed x86_64 and i386 input test 1"