From 72e9d41dcc6439963349749d3775db4b27a7d386 Mon Sep 17 00:00:00 2001
From: Fabian Homborg <FHomborg@gmail.com>
Date: Fri, 1 Jun 2018 20:14:29 +0200
Subject: [PATCH] [complete] Fix crash with __fish_describe_command

Our completion machinery calls our `__fish_describe_command` function
to describe commands via apropos. Only it trusts the output a bit too
much, so it crashes when any line from that is shorter than the
original string.

Fix this by skipping any string that is shorter than the original,
since it can't be a match anyway.

Also stop doing wcslen so often - std::strings are nice!

Fixes #5014.
---
 src/complete.cpp | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/complete.cpp b/src/complete.cpp
index a5dad891d..3b3e8ef0b 100644
--- a/src/complete.cpp
+++ b/src/complete.cpp
@@ -542,20 +542,19 @@ void completer_t::complete_strings(const wcstring &wc_escaped, const wchar_t *de
 void completer_t::complete_cmd_desc(const wcstring &str) {
     ASSERT_IS_MAIN_THREAD();
 
-    const wchar_t *cmd_start;
-    const wchar_t *const cmd = str.c_str();
-    cmd_start = wcsrchr(cmd, L'/');
-
-    if (cmd_start)
-        cmd_start++;
-    else
-        cmd_start = cmd;
+    wcstring cmd;
+    size_t pos = str.find_last_of(L'/');
+    if (pos != std::string::npos) {
+        cmd = wcstring(str, pos);
+    } else {
+        cmd = str;
+    }
 
     // Using apropos with a single-character search term produces far to many results - require at
     // least two characters if we don't know the location of the whatis-database.
-    if (wcslen(cmd_start) < 2) return;
+    if (cmd.length() < 2) return;
 
-    if (wildcard_has(cmd_start, 0)) {
+    if (wildcard_has(cmd, 0)) {
         return;
     }
 
@@ -572,7 +571,7 @@ void completer_t::complete_cmd_desc(const wcstring &str) {
     }
 
     wcstring lookup_cmd(L"__fish_describe_command ");
-    lookup_cmd.append(escape_string(cmd_start, 1));
+    lookup_cmd.append(escape_string(cmd, 1));
 
     // First locate a list of possible descriptions using a single call to apropos or a direct
     // search if we know the location of the whatis database. This can take some time on slower
@@ -589,7 +588,8 @@ void completer_t::complete_cmd_desc(const wcstring &str) {
         // mqudsi: I don't know if the above were ever true, but it's certainly not any more.
         // Plenty of allocations below.
         for (const wcstring &elstr : list) {
-            const wcstring fullkey(elstr, wcslen(cmd_start));
+            if (elstr.length() < cmd.length()) continue;
+            const wcstring fullkey(elstr, cmd.length());
 
             size_t tab_idx = fullkey.find(L'\t');
             if (tab_idx == wcstring::npos) continue;