[binutils-gdb] gdb/python: avoid depending on the curses library

[Andrew Burgess]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5ddd0d7eefbb683a09e233b7dfb4a48a04b72b8e

commit 5ddd0d7eefbb683a09e233b7dfb4a48a04b72b8e
Author: Andrew Burgess <aburgess@redhat.com>
Date:   Mon Sep 9 17:33:54 2024 +0100

    gdb/python: avoid depending on the curses library
    
    The commit:
    
      commit 29c70787112e01cd52b53bf14bdcacb0a11e0725
      Date:   Sun Sep 8 07:46:09 2024 +0200
    
          [gdb/testsuite] Handle missing curses in gdb.python/py-missing-debug.exp
    
    Highlighted that in some cases we might be running on a system with an
    older version of Python (earlier than 3.7), and on a system for which
    the curses library has not been installed.
    
    In these circumstances the gdb.missing_debug module will not load as
    it uses curses to provide isalnum() and isascii() functions.
    
    To avoid this problem I propose that we copy the isalnum() and
    isascii() from the Python curses library.  These functions are
    basically trivial and removing the curses dependency means GDB will
    work in more cases without increasing its dependencies.
    
    I did consider keeping the uses of curses and only having the function
    definitions be a fallback for when the curses library failed to load,
    but this felt like overkill.  The function definitions are both tiny
    and I think "obvious" given their specifications, so I figure we might
    as well just use our own definitions if they are not available as
    builtin methods on the str class.
    
    For testing I changed this line:
    
      if sys.version_info >= (3, 7):
    
    to
    
      if sys.version_info >= (3, 7) and False:
    
    then reran gdb.python/py-missing-debug.exp, there were no failures.
    
    Approved-By: Tom de Vries <tdevries@suse.de>

Diff:
---
 gdb/python/lib/gdb/missing_debug.py | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/gdb/python/lib/gdb/missing_debug.py b/gdb/python/lib/gdb/missing_debug.py
index 6d57462c185..7ccc4fe496d 100644
--- a/gdb/python/lib/gdb/missing_debug.py
+++ b/gdb/python/lib/gdb/missing_debug.py
@@ -31,9 +31,33 @@ if sys.version_info >= (3, 7):
         return ch.isalnum()
 
 else:
-    # Fall back to curses.ascii.isascii() and curses.ascii.isalnum() for
-    # earlier versions.
-    from curses.ascii import isalnum, isascii
+    # Older version of Python doesn't have str.isascii() and
+    # str.isalnum() so provide our own.
+    #
+    # We could import isalnum() and isascii() from the curses library,
+    # but that adds an extra dependency.  Given these functions are
+    # both small and trivial lets implement them here.
+    #
+    # These definitions are based on those in the curses library, but
+    # simplified as we know C will always be a single character 'str'.
+
+    def isdigit(c):
+        return 48 <= ord(c) <= 57
+
+    def islower(c):
+        return 97 <= ord(c) <= 122
+
+    def isupper(c):
+        return 65 <= ord(c) <= 90
+
+    def isalpha(c):
+        return isupper(c) or islower(c)
+
+    def isalnum(c):
+        return isalpha(c) or isdigit(c)
+
+    def isascii(c):
+        return 0 <= ord(c) <= 127
 
 
 def _validate_name(name):