From 9ee5892798be81f7a6f3e070ecd52cbf0d55740e Mon Sep 17 00:00:00 2001
From: Denys Vlasenko
Date: Mon, 17 Feb 2020 10:24:32 +0100
Subject: ash: expand: Fix trailing newlines processing in backquote expanding

Upstream commit:

    Date: Mon, 29 Apr 2019 19:13:37 +0500
    expand: Fix trailing newlines processing in backquote expanding

    According to POSIX.1-2008 we should remove newlines only at the end of
    the substitution. Newlines-only substitions causes dash to remove
    newlines before beggining of the substitution. The following code:

        cat <<END
        1
        $(echo "")
        2
        END

    prints "1<newline>2" instead of expected "1<newline><newline>2".

    This patch fixes trailing newlines processing in backquote expanding.

    Signed-off-by: Nikolai Merinov <n.merinov@inango-systems.com>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
 shell/ash.c                                       | 2 +-
 shell/ash_test/ash-psubst/tick_in_heredoc.right   | 5 +++++
 shell/ash_test/ash-psubst/tick_in_heredoc.tests   | 7 +++++++
 shell/hush_test/hush-psubst/tick_in_heredoc.right | 5 +++++
 shell/hush_test/hush-psubst/tick_in_heredoc.tests | 7 +++++++
 5 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 shell/ash_test/ash-psubst/tick_in_heredoc.right
 create mode 100755 shell/ash_test/ash-psubst/tick_in_heredoc.tests
 create mode 100644 shell/hush_test/hush-psubst/tick_in_heredoc.right
 create mode 100755 shell/hush_test/hush-psubst/tick_in_heredoc.tests

diff --git a/shell/ash.c b/shell/ash.c
index 90496ba..dfe6d1c 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6578,7 +6578,7 @@ expbackq(union node *cmd, int flag)
 
 	/* Eat all trailing newlines */
 	dest = expdest;
-	for (; dest > (char *)stackblock() && dest[-1] == '\n';)
+	for (; dest > ((char *)stackblock() + startloc) && dest[-1] == '\n';)
 		STUNPUTC(dest);
 	expdest = dest;
 
diff --git a/shell/ash_test/ash-psubst/tick_in_heredoc.right b/shell/ash_test/ash-psubst/tick_in_heredoc.right
new file mode 100644
index 0000000..7e7bac6
--- /dev/null
+++ b/shell/ash_test/ash-psubst/tick_in_heredoc.right
@@ -0,0 +1,5 @@
+1
+
+2
+
+3
diff --git a/shell/ash_test/ash-psubst/tick_in_heredoc.tests b/shell/ash_test/ash-psubst/tick_in_heredoc.tests
new file mode 100755
index 0000000..c8eb8f4
--- /dev/null
+++ b/shell/ash_test/ash-psubst/tick_in_heredoc.tests
@@ -0,0 +1,7 @@
+cat <<END
+1
+$(echo "")
+2
+`echo ""`
+3
+END
diff --git a/shell/hush_test/hush-psubst/tick_in_heredoc.right b/shell/hush_test/hush-psubst/tick_in_heredoc.right
new file mode 100644
index 0000000..7e7bac6
--- /dev/null
+++ b/shell/hush_test/hush-psubst/tick_in_heredoc.right
@@ -0,0 +1,5 @@
+1
+
+2
+
+3
diff --git a/shell/hush_test/hush-psubst/tick_in_heredoc.tests b/shell/hush_test/hush-psubst/tick_in_heredoc.tests
new file mode 100755
index 0000000..c8eb8f4
--- /dev/null
+++ b/shell/hush_test/hush-psubst/tick_in_heredoc.tests
@@ -0,0 +1,7 @@
+cat <<END
+1
+$(echo "")
+2
+`echo ""`
+3
+END
-- 
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