[PATCH] ar: Add --thin for creating thin archives

[Fangrui Song]

In many ar implementations (FreeBSD, elfutils, etc), ar -T has the
X/Open System Interface specified semantics. Therefore -T for thin
archives is not recommended for portability.

    PR binutils/28759
    * ar.c (long_options): Add --thin.
    * binutils/testsuite/binutils-all/ar.exp: Add tests.
    * NEWS: Mention --thin.
---
 binutils/NEWS                          |  4 ++++
 binutils/ar.c                          |  1 +
 binutils/testsuite/binutils-all/ar.exp | 17 +++++++++++++++++
 3 files changed, 22 insertions(+)

diff --git a/binutils/NEWS b/binutils/NEWS
index 903f8233b99..9598930b581 100644
--- a/binutils/NEWS
+++ b/binutils/NEWS
@@ -18,6 +18,10 @@
 * Support for efi-app-aarch64, efi-rtdrv-aarch64 and efi-bsdrv-aarch64 has been
   added to objcopy in order to enable UEFI development using binutils.
 
+* ar: Add --thin for creating thin archives. -T is not recommended for
+  portability because in many ar implementations -T has a different meaning
+  from X/Open System Interface.
+
 Changes in 2.37:
 
 * The readelf tool has a new command line option which can be used to specify
diff --git a/binutils/ar.c b/binutils/ar.c
index d7d2fc21dd9..ba710ee426d 100644
--- a/binutils/ar.c
+++ b/binutils/ar.c
@@ -172,6 +172,7 @@ static struct option long_options[] =
   {"version", no_argument, &show_version, 1},
   {"output", required_argument, NULL, OPTION_OUTPUT},
   {"record-libdeps", required_argument, NULL, 'l'},
+  {"thin", no_argument, NULL, 'T'},
   {NULL, no_argument, NULL, 0}
 };
 
diff --git a/binutils/testsuite/binutils-all/ar.exp b/binutils/testsuite/binutils-all/ar.exp
index 12aa079865b..3b841825f6f 100644
--- a/binutils/testsuite/binutils-all/ar.exp
+++ b/binutils/testsuite/binutils-all/ar.exp
@@ -309,11 +309,13 @@ proc thin_archive_with_nested { bfdtests } {
     if [is_remote host] {
 	set archive artest.a
 	set archive2 artest2.a
+	set archive3 artest3.a
 	set objfile [remote_download host tmpdir/bintest.${obj}]
 	remote_file host delete $archive
     } else {
 	set archive tmpdir/artest.a
 	set archive2 tmpdir/artest2.a
+	set archive3 tmpdir/artest3.a
 	set objfile tmpdir/bintest.${obj}
     }
 
@@ -333,6 +335,14 @@ proc thin_archive_with_nested { bfdtests } {
 	return
     }
 
+    remote_file build delete tmpdir/artest3.a
+
+    set got [binutils_run $AR "rc --thin $archive3 ${archive}"]
+    if ![string match "" $got] {
+	fail $testname
+	return
+    }
+
     foreach bfdtest $bfdtests {
 	set exec_output [binutils_run "$base_dir/$bfdtest" "$archive"]
 	if ![string match "" $exec_output] {
@@ -347,6 +357,13 @@ proc thin_archive_with_nested { bfdtests } {
 	    fail "$testname ($bfdtest)"
 	    return
 	}
+
+	set exec_output [binutils_run "$base_dir/$bfdtest" "$archive3"]
+	if ![string match "" $exec_output] {
+	    verbose -log $exec_output
+	    fail "$testname ($bfdtest)"
+	    return
+	}
     }
 
     set got [binutils_run $NM "--print-armap $archive"]
-- 
2.34.1.575.g55b058a8bb-goog