[binutils-gdb] Handle "set height 1"

[binutils-gdb] Handle "set height 1"

[Tom Tromey]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=111d19818a4a7c96c87e330c6c143fa03bb86819

commit 111d19818a4a7c96c87e330c6c143fa03bb86819
Author: Tom Tromey <tom@tromey.com>
Date:   Sat Jan 8 19:37:38 2022 -0700

    Handle "set height 1"
    
    PR cli/17151 points out that "set height 1" has pathological behavior
    in gdb.  What I see is that gdb will endlessly print the pagination
    prompt.  This patch takes a simple and expedient approach to a fix:
    pretend that the height is really 2.
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=17151

Diff:
---
 gdb/testsuite/gdb.base/page.exp |  7 ++++---
 gdb/utils.c                     | 10 ++++++++--
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/gdb/testsuite/gdb.base/page.exp b/gdb/testsuite/gdb.base/page.exp
index a38f1dd0c94..268777f8acb 100644
--- a/gdb/testsuite/gdb.base/page.exp
+++ b/gdb/testsuite/gdb.base/page.exp
@@ -121,6 +121,7 @@ foreach_with_prefix size {"0" "0x80000000" "unlimited"} {
 gdb_test "set width -1" "integer -1 out of range"
 gdb_test "set height -1" "integer -1 out of range"
 
-gdb_exit
-return 0
-
+# A height of 1 used to cause pathological behavior -- it would
+# endlessly prompt for paging without printing anything.
+gdb_test_no_output "set height 1"
+gdb_test "print 23" " = 23"
diff --git a/gdb/utils.c b/gdb/utils.c
index b7d5859d6b3..2465bf3a3ed 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -1601,6 +1601,12 @@ pager_file::puts (const char *linebuffer)
 			 m_wrap_indent = 0;
 		       });
 
+  /* If the user does "set height 1" then the pager will exhibit weird
+     behavior.  This is pathological, though, so don't allow it.  */
+  const unsigned int lines_allowed = (lines_per_page > 1
+				      ? lines_per_page - 1
+				      : 1);
+
   /* Go through and output each character.  Show line extension
      when this is necessary; prompt user for new page when this is
      necessary.  */
@@ -1613,7 +1619,7 @@ pager_file::puts (const char *linebuffer)
 	 it here.  */
       if (pagination_enabled
 	  && !pagination_disabled_for_command
-	  && lines_printed >= lines_per_page - 1)
+	  && lines_printed >= lines_allowed)
 	prompt_for_continue ();
 
       while (*lineptr && *lineptr != '\n')
@@ -1690,7 +1696,7 @@ pager_file::puts (const char *linebuffer)
 		 this loop, so we must continue to check it here.  */
 	      if (pagination_enabled
 		  && !pagination_disabled_for_command
-		  && lines_printed >= lines_per_page - 1)
+		  && lines_printed >= lines_allowed)
 		{
 		  prompt_for_continue ();
 		  did_paginate = true;