[groff] 06/27: [troff]: Fix backtrace output in degenerate case.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit 2fc5508dd89fbd821f6899c94a778fe5c5c1f6bd
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Sun May 1 22:32:30 2022 -0500

    [troff]: Fix backtrace output in degenerate case.
    
    * src/roff/troff/input.cpp (string_iterator::backtrace): Fix spurious
      output when `mac.filename` is empty.  Provoked by:
        $ printf '\\(' | troff
---
 ChangeLog                | 6 ++++++
 src/roff/troff/input.cpp | 4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 20d6e879..64b3304c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2022-05-01  G. Branden Robinson <g.branden.robinson@gmail.com>
+
+       * src/roff/troff/input.cpp (string_iterator::backtrace): Fix
+       spurious output when `mac.filename` is empty.  Provoked by:
+         $ printf '\\(' | troff
+
 2022-05-01  G. Branden Robinson <g.branden.robinson@gmail.com>
 
        * src/preproc/refer/refer.cpp: Trivially refactor.  Demote
diff --git a/src/roff/troff/input.cpp b/src/roff/troff/input.cpp
index 029bfad8..80959fd4 100644
--- a/src/roff/troff/input.cpp
+++ b/src/roff/troff/input.cpp
@@ -3579,9 +3579,9 @@ int string_iterator::get_location(int allow_macro,
 
 void string_iterator::backtrace()
 {
-  if (program_name)
-    fprintf(stderr, "%s: ", program_name);
   if (mac.filename) {
+    if (program_name)
+      fprintf(stderr, "%s: ", program_name);
     errprint("backtrace: '%1':%2", mac.filename,
             mac.lineno + lineno - 1);
     if (how_invoked) {