From a1cdb1543604cf00db89b31cffd4797b50760a9a Mon Sep 17 00:00:00 2001
From: "G. Branden Robinson" <g.branden.robinson@gmail.com>
Date: Thu, 7 Mar 2024 10:20:17 -0600
Subject: [troff]: Fix Savannah #65427 (check fp==nullptr).

* src/roff/troff/node.cpp (ascii_output_file::outc)
  (ascii_output_file::outs, put_string, troff_output_file::put)
  (ascii_output_file::really_transparent_char)
  (ascii_output_file::really_print_line): Guard uses of standard C
  library `putc()` and `fputc()` functions with a null pointer check.
  They could fail if the output stream has been invalidated.  Problem
  present from groff's birth and apparently exposed by man-db man's use
  of AppArmor.  See
  <https://bugs.launchpad.net/ubuntu/+source/lintian/+bug/2055402> and
  follow-up discussion there.

Fixes <https://savannah.gnu.org/bugs/?65427>.  Thanks to an anonymous
submitter for the report.

No apparent performance degradation, even _without_ optimization, on
20 rebuilds of automake.pdf, contrib/mom/examples/*.pdf, and
groff-man-pages.pdf.

CFLAGS="-O0 -Og -ggdb"

Before:
+ awk /Elapsed/ {time = $NF; sub("0:", "", time); print time}
+ datamash range 1 mean 1 sstdev 1
3.35    11.0475 1.0103510333178

After:
+ awk /Elapsed/ {time = $NF; sub("0:", "", time); print time}
+ datamash range 1 mean 1 sstdev 1
2.49    10.81380952381  0.62027797148114

Origin: upstream, https://git.savannah.gnu.org/cgit/groff.git/commit/?id=5c923303a9ef44bb4bc4f44d09799f93193fc079
Bug: https://savannah.gnu.org/bugs/?65427
Last-Update: 2024-07-04

Patch-Name: check-fp.patch
---
 src/roff/troff/node.cpp | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/roff/troff/node.cpp b/src/roff/troff/node.cpp
index d17198db8..f3395413e 100644
--- a/src/roff/troff/node.cpp
+++ b/src/roff/troff/node.cpp
@@ -770,15 +770,18 @@ public:
 
 void ascii_output_file::outc(unsigned char c)
 {
-  fputc(c, fp);
+  if (fp != 0 /* nullptr */)
+    fputc(c, fp);
 }
 
 void ascii_output_file::outs(const char *s)
 {
-  fputc('<', fp);
-  if (s)
-    fputs(s, fp);
-  fputc('>', fp);
+  if (fp != 0 /* nullptr */) {
+    fputc('<', fp);
+    if (s)
+      fputs(s, fp);
+    fputc('>', fp);
+  }
 }
 
 struct hvpair;
@@ -848,18 +851,22 @@ public:
 
 static void put_string(const char *s, FILE *fp)
 {
-  for (; *s != '\0'; ++s)
-    putc(*s, fp);
+  if (fp != 0 /* nullptr */) {
+    for (; *s != '\0'; ++s)
+      putc(*s, fp);
+  }
 }
 
 inline void troff_output_file::put(char c)
 {
-  putc(c, fp);
+  if (fp != 0 /* nullptr */)
+    putc(c, fp);
 }
 
 inline void troff_output_file::put(unsigned char c)
 {
-  putc(c, fp);
+  if (fp != 0 /* nullptr */)
+    putc(c, fp);
 }
 
 inline void troff_output_file::put(const char *s)
@@ -1790,7 +1797,8 @@ void real_output_file::really_off()
 
 void ascii_output_file::really_transparent_char(unsigned char c)
 {
-  putc(c, fp);
+  if (fp != 0 /* nullptr */)
+    putc(c, fp);
 }
 
 void ascii_output_file::really_print_line(hunits, vunits, node *n,
@@ -1800,7 +1808,8 @@ void ascii_output_file::really_print_line(hunits, vunits, node *n,
     n->ascii_print(this);
     n = n->next;
   }
-  fputc('\n', fp);
+  if (fp != 0 /* nullptr */)
+    fputc('\n', fp);
 }
 
 void ascii_output_file::really_begin_page(int /*pageno*/, vunits /*page_length*/)