[Buildroot] [PATCH v2] package/openssh: fix '-fzero-call-used-regs' option support detection

[Peter Seiderer]

- add upstream patch ([1]) to fix '-fzero-call-used-regs' gcc compiler option
  support detection

- add autoreconf as the patch touches m4/openssh.m4

Fixes:

  - https://bugs.busybox.net/show_bug.cgi?id=14651

  bitmap.c: In function ‘reserve’:
  bitmap.c:98:1: sorry, unimplemented: ‘-fzero-call-used-regs’ not supported on this target
     98 | }
        | ^

[1] https://github.com/openssh/openssh-portable/commit/f107467179428a0e3ea9e4aa9738ac12ff02822d.patch

Signed-off-by: Peter Seiderer <ps.report at gmx.net>
---
Changes v1 -> v2:
  - rebased and renumbered patch from 0001-Improve-detection-of-fzero-call-used-regs-all-suppor.patch
    to 0002-Improve-detection-of-fzero-call-used-regs-all-suppor.patch
---
 ...n-of-fzero-call-used-regs-all-suppor.patch | 38 +++++++++++++++++++
 package/openssh/openssh.mk                    |  4 ++
 2 files changed, 42 insertions(+)
 create mode 100644 package/openssh/0002-Improve-detection-of-fzero-call-used-regs-all-suppor.patch

diff --git a/package/openssh/0002-Improve-detection-of-fzero-call-used-regs-all-suppor.patch b/package/openssh/0002-Improve-detection-of-fzero-call-used-regs-all-suppor.patch
new file mode 100644
index 0000000000..ce5c5539ff
--- /dev/null
+++ b/package/openssh/0002-Improve-detection-of-fzero-call-used-regs-all-suppor.patch
@@ -0,0 +1,38 @@
+From b5fee5fe98f708c1dc61a1564db35eacadbfe8b3 Mon Sep 17 00:00:00 2001
+From: Colin Watson <cjwatson at debian.org>
+Date: Thu, 24 Feb 2022 16:04:18 +0000
+Subject: [PATCH] Improve detection of -fzero-call-used-regs=all support
+
+GCC doesn't tell us whether this option is supported unless it runs into
+the situation where it would need to emit corresponding code.
+
+[Upstream: https://github.com/openssh/openssh-portable/commit/f107467179428a0e3ea9e4aa9738ac12ff02822d.patch]
+Signed-off-by: Peter Seiderer <ps.report at gmx.net>
+---
+ m4/openssh.m4 | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/m4/openssh.m4 b/m4/openssh.m4
+index 4f9c379..8c33c70 100644
+--- a/m4/openssh.m4
++++ b/m4/openssh.m4
+@@ -14,6 +14,8 @@ AC_DEFUN([OSSH_CHECK_CFLAG_COMPILE], [{
+ 	AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+ #include <stdlib.h>
+ #include <stdio.h>
++/* Trivial function to help test for -fzero-call-used-regs */
++void f(int n) {}
+ int main(int argc, char **argv) {
+ 	(void)argv;
+ 	/* Some math to catch -ftrapv problems in the toolchain */
+@@ -21,6 +23,7 @@ int main(int argc, char **argv) {
+ 	float l = i * 2.1;
+ 	double m = l / 0.5;
+ 	long long int n = argc * 12345LL, o = 12345LL * (long long int)argc;
++	f(0);
+ 	printf("%d %d %d %f %f %lld %lld\n", i, j, k, l, m, n, o);
+ 	/*
+ 	 * Test fallthrough behaviour.  clang 10's -Wimplicit-fallthrough does
+-- 
+2.35.1
+
diff --git a/package/openssh/openssh.mk b/package/openssh/openssh.mk
index 0e0d59e6ab..84add9563d 100644
--- a/package/openssh/openssh.mk
+++ b/package/openssh/openssh.mk
@@ -12,6 +12,10 @@ OPENSSH_CPE_ID_UPDATE = $(OPENSSH_VERSION_MINOR)
 OPENSSH_SITE = http://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable
 OPENSSH_LICENSE = BSD-3-Clause, BSD-2-Clause, Public Domain
 OPENSSH_LICENSE_FILES = LICENCE
+
+# patch touching m4/openssh.m4
+OPENSSH_AUTORECONF = YES
+
 OPENSSH_CONF_ENV = \
 	LD="$(TARGET_CC)" \
 	LDFLAGS="$(TARGET_CFLAGS)" \
-- 
2.35.1