Add support for hex int literals.

docs/markdown/Syntax.md

@@ -58,6 +58,12 @@ y = 3 * 4
 d = 5 % 3 # Yields 2.
 ```
 
+Hexadecimal literals are supported since version 0.45.0:
+
+```meson
+int_255 = 0xFF
+```
+
 Strings can be converted to a number like this:
 
 ```meson

docs/markdown/snippets/hexnumbers.md

@@ -0,0 +1,5 @@
+## Hexadecimal string literals
+
+Hexadecimal integer literals can now be used in build and option files.
+
+    int_255 = 0xFF

mesonbuild/mparser.py

@@ -71,6 +71,7 @@ class Lexer:
             # Need to be sorted longest to shortest.
             ('ignore', re.compile(r'[ \t]')),
             ('id', re.compile('[_a-zA-Z][_0-9a-zA-Z]*')),
+            ('hexnumber', re.compile('0[xX][0-9a-fA-F]+')),
             ('number', re.compile(r'\d+')),
             ('eol_cont', re.compile(r'\\\n')),
             ('eol', re.compile(r'\n')),
@@ -152,6 +153,9 @@ class Lexer:
                             line_start = mo.end() - len(lines[-1])
                     elif tid == 'number':
                         value = int(match_text)
+                    elif tid == 'hexnumber':
+                        tid = 'number'
+                        value = int(match_text, base=16)
                     elif tid == 'eol' or tid == 'eol_cont':
                         lineno += 1
                         line_start = loc

test cases/common/68 number arithmetic/meson.build

@@ -56,3 +56,9 @@ assert(3 >= 3, 'Gte broken')
 
 assert(true.to_int() == 1,'bool to_int() broken')
 assert(false.to_int() == 0,'bool to_int() broken')
+
+hex_255 = 0xff
+hex2_255 = 0XFF
+
+assert(hex_255 == 255, 'Hex parsing is broken.')
+assert(hex2_255 == 255, 'Uppercase hex parsing is broken.')