diff --git a/CHANGES.current b/CHANGES.current
index 59257dc09..028adcf74 100644
--- a/CHANGES.current
+++ b/CHANGES.current
@@ -7,6 +7,15 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2022-01-25: olly
+	    #80 #635 https://sourceforge.net/p/swig/bugs/1139/
+	    Add support for parsing common cases of `<` and `>` comparisons
+	    in constant expressions.  Adding full support for these seems hard
+	    to do without introducing conflicts into the parser grammar, but in
+	    fact all reported cases have had parentheses around the comparison
+	    and we can support that with a few restrictions on the left side of
+	    `<`.
+
 2022-01-25: wsfulton
             New warning 327 for extern templates, eg:
 
diff --git a/Examples/test-suite/common.mk b/Examples/test-suite/common.mk
index 5a44980cc..6574c4549 100644
--- a/Examples/test-suite/common.mk
+++ b/Examples/test-suite/common.mk
@@ -141,6 +141,7 @@ CPP_TEST_CASES += \
 	compactdefaultargs \
 	const_const_2 \
 	constant_directive \
+	constant_expr \
 	constant_pointers \
 	constover \
 	constructor_copy \
@@ -689,7 +690,7 @@ C_TEST_CASES += \
 	c_delete_function \
 	char_constant \
 	const_const \
-	constant_expr \
+	constant_expr_c \
 	default_args_c \
 	empty_c \
 	enums \
diff --git a/Examples/test-suite/constant_expr.i b/Examples/test-suite/constant_expr.i
index 8e5c8aee6..7cb529f8a 100644
--- a/Examples/test-suite/constant_expr.i
+++ b/Examples/test-suite/constant_expr.i
@@ -1,11 +1,17 @@
 %module constant_expr;
-/* Tests of constant expressions. */
+/* Tests of constant expressions (C++ version). */
+
+%include "constant_expr_c.i"
 
 %inline %{
 
-/* % didn't work in SWIG 1.3.40 and earlier. */
-const int X = 123%7;
-#define FOO 12 % 9
-double d_array[12 % 9];
+// Testcase from https://sourceforge.net/p/swig/bugs/1139/
+template<typename Tp>
+struct SizeInfo {
+enum {
+isLarge = (sizeof(Tp)>sizeof(void*)),
+isPointer = false
+};
+};
 
 %}
diff --git a/Examples/test-suite/constant_expr_c.i b/Examples/test-suite/constant_expr_c.i
new file mode 100644
index 000000000..b7431c1f1
--- /dev/null
+++ b/Examples/test-suite/constant_expr_c.i
@@ -0,0 +1,35 @@
+%module constant_expr_c;
+/* Tests of constant expressions (C version). */
+
+%inline %{
+
+/* % didn't work in SWIG 1.3.40 and earlier. */
+const int X = 123%7;
+#define FOO 12 % 9
+double d_array[12 % 9];
+
+/* `<` and `>` in constant expressions caused parse errors before SWIG 4.1.0.
+ * They're now supported if inside parentheses (and with some restrictions
+ * on the LHS of `<`.
+ */
+
+// Testcase from https://github.com/swig/swig/issues/635
+#define TEST_A 1
+#define TEST_B 2
+#define TEST_C (TEST_A < TEST_B)
+#define TEST_D (TEST_A > TEST_B)
+// These have been supported since 1.3.41.
+#define TEST_E (TEST_A <= TEST_B)
+#define TEST_F (TEST_A >= TEST_B)
+// For completeness
+#define TEST_G (TEST_A == TEST_B)
+#define TEST_H (TEST_A != TEST_B)
+
+// No warning
+#if (TEST_A < TEST_B)
+#define TEST_I 1
+#else
+#define TEST_I 0
+#endif
+
+%}
diff --git a/Examples/test-suite/csharp/preproc_constants_c_runme.cs b/Examples/test-suite/csharp/preproc_constants_c_runme.cs
index 5966d5266..8cdb705c9 100644
--- a/Examples/test-suite/csharp/preproc_constants_c_runme.cs
+++ b/Examples/test-suite/csharp/preproc_constants_c_runme.cs
@@ -51,6 +51,8 @@ public class runme {
     assert( typeof(int) == preproc_constants_c.EXPR_MINUS.GetType() );
     assert( typeof(int) == preproc_constants_c.EXPR_LSHIFT.GetType() );
     assert( typeof(int) == preproc_constants_c.EXPR_RSHIFT.GetType() );
+    assert( typeof(int) == preproc_constants_c.EXPR_LT.GetType() );
+    assert( typeof(int) == preproc_constants_c.EXPR_GT.GetType() );
     assert( typeof(int) == preproc_constants_c.EXPR_LTE.GetType() );
     assert( typeof(int) == preproc_constants_c.EXPR_GTE.GetType() );
     assert( typeof(int) == preproc_constants_c.EXPR_INEQUALITY.GetType() );
diff --git a/Examples/test-suite/csharp/preproc_constants_runme.cs b/Examples/test-suite/csharp/preproc_constants_runme.cs
index 6af8f20a4..d79e2c302 100644
--- a/Examples/test-suite/csharp/preproc_constants_runme.cs
+++ b/Examples/test-suite/csharp/preproc_constants_runme.cs
@@ -50,6 +50,8 @@ public class runme {
     assert( typeof(int) == preproc_constants.EXPR_MINUS.GetType() );
     assert( typeof(int) == preproc_constants.EXPR_LSHIFT.GetType() );
     assert( typeof(int) == preproc_constants.EXPR_RSHIFT.GetType() );
+    assert( typeof(bool) == preproc_constants.EXPR_LT.GetType() );
+    assert( typeof(bool) == preproc_constants.EXPR_GT.GetType() );
     assert( typeof(bool) == preproc_constants.EXPR_LTE.GetType() );
     assert( typeof(bool) == preproc_constants.EXPR_GTE.GetType() );
     assert( typeof(bool) == preproc_constants.EXPR_INEQUALITY.GetType() );
diff --git a/Examples/test-suite/d/preproc_constants_c_runme.1.d b/Examples/test-suite/d/preproc_constants_c_runme.1.d
index a6c2f3d10..f98f37b5f 100644
--- a/Examples/test-suite/d/preproc_constants_c_runme.1.d
+++ b/Examples/test-suite/d/preproc_constants_c_runme.1.d
@@ -51,6 +51,8 @@ void main() {
   static assert(is(int == typeof(EXPR_MINUS())));
   static assert(is(int == typeof(EXPR_LSHIFT())));
   static assert(is(int == typeof(EXPR_RSHIFT())));
+  static assert(is(int == typeof(EXPR_LT())));
+  static assert(is(int == typeof(EXPR_GT())));
   static assert(is(int == typeof(EXPR_LTE())));
   static assert(is(int == typeof(EXPR_GTE())));
   static assert(is(int == typeof(EXPR_INEQUALITY())));
diff --git a/Examples/test-suite/d/preproc_constants_c_runme.2.d b/Examples/test-suite/d/preproc_constants_c_runme.2.d
index 786cb48cc..caf3029b2 100644
--- a/Examples/test-suite/d/preproc_constants_c_runme.2.d
+++ b/Examples/test-suite/d/preproc_constants_c_runme.2.d
@@ -51,6 +51,8 @@ void main() {
   static assert(is(int == typeof(EXPR_MINUS())));
   static assert(is(int == typeof(EXPR_LSHIFT())));
   static assert(is(int == typeof(EXPR_RSHIFT())));
+  static assert(is(int == typeof(EXPR_LT())));
+  static assert(is(int == typeof(EXPR_GT())));
   static assert(is(int == typeof(EXPR_LTE())));
   static assert(is(int == typeof(EXPR_GTE())));
   static assert(is(int == typeof(EXPR_INEQUALITY())));
diff --git a/Examples/test-suite/d/preproc_constants_runme.1.d b/Examples/test-suite/d/preproc_constants_runme.1.d
index 85fa918e4..95f3c4757 100644
--- a/Examples/test-suite/d/preproc_constants_runme.1.d
+++ b/Examples/test-suite/d/preproc_constants_runme.1.d
@@ -50,6 +50,8 @@ void main() {
   static assert(is(int == typeof(EXPR_MINUS())));
   static assert(is(int == typeof(EXPR_LSHIFT())));
   static assert(is(int == typeof(EXPR_RSHIFT())));
+  static assert(is(int == typeof(EXPR_LT())));
+  static assert(is(int == typeof(EXPR_GT())));
   static assert(is(bool == typeof(EXPR_LTE())));
   static assert(is(bool == typeof(EXPR_GTE())));
   static assert(is(bool == typeof(EXPR_INEQUALITY())));
diff --git a/Examples/test-suite/d/preproc_constants_runme.2.d b/Examples/test-suite/d/preproc_constants_runme.2.d
index c81e53160..416384a11 100644
--- a/Examples/test-suite/d/preproc_constants_runme.2.d
+++ b/Examples/test-suite/d/preproc_constants_runme.2.d
@@ -50,6 +50,8 @@ void main() {
   static assert(is(int == typeof(EXPR_MINUS())));
   static assert(is(int == typeof(EXPR_LSHIFT())));
   static assert(is(int == typeof(EXPR_RSHIFT())));
+  static assert(is(bool == typeof(EXPR_LT())));
+  static assert(is(bool == typeof(EXPR_GT())));
   static assert(is(bool == typeof(EXPR_LTE())));
   static assert(is(bool == typeof(EXPR_GTE())));
   static assert(is(bool == typeof(EXPR_INEQUALITY())));
diff --git a/Examples/test-suite/php/preproc_constants_c_runme.php b/Examples/test-suite/php/preproc_constants_c_runme.php
index 411f7d766..688da52f6 100644
--- a/Examples/test-suite/php/preproc_constants_c_runme.php
+++ b/Examples/test-suite/php/preproc_constants_c_runme.php
@@ -51,6 +51,8 @@ check::equal(gettype(preproc_constants_c::EXPR_PLUS), "integer", "preproc_consta
 check::equal(gettype(preproc_constants_c::EXPR_MINUS), "integer", "preproc_constants.EXPR_MINUS has unexpected type");
 check::equal(gettype(preproc_constants_c::EXPR_LSHIFT), "integer", "preproc_constants.EXPR_LSHIFT has unexpected type");
 check::equal(gettype(preproc_constants_c::EXPR_RSHIFT), "integer", "preproc_constants.EXPR_RSHIFT has unexpected type");
+check::equal(gettype(preproc_constants_c::EXPR_LT), "integer", "preproc_constants.EXPR_LTE has unexpected type");
+check::equal(gettype(preproc_constants_c::EXPR_GT), "integer", "preproc_constants.EXPR_GTE has unexpected type");
 check::equal(gettype(preproc_constants_c::EXPR_LTE), "integer", "preproc_constants.EXPR_LTE has unexpected type");
 check::equal(gettype(preproc_constants_c::EXPR_GTE), "integer", "preproc_constants.EXPR_GTE has unexpected type");
 check::equal(gettype(preproc_constants_c::EXPR_INEQUALITY), "integer", "preproc_constants.EXPR_INEQUALITY has unexpected type");
diff --git a/Examples/test-suite/preproc_constants.i b/Examples/test-suite/preproc_constants.i
index 3050baa06..f0c5e9361 100644
--- a/Examples/test-suite/preproc_constants.i
+++ b/Examples/test-suite/preproc_constants.i
@@ -72,10 +72,8 @@
 
 #define EXPR_LSHIFT      0xFF << 2
 #define EXPR_RSHIFT      0xFF >> 2
-/* FIXME
-#define EXPR_LT          0xFF < 255
-#define EXPR_GT          0xFF > 255
-*/
+#define EXPR_LT          (0xFF < 255)
+#define EXPR_GT          (0xFF > 255)
 #define EXPR_LTE         0xFF <= 255
 #define EXPR_GTE         0xFF >= 255
 #define EXPR_INEQUALITY  0xFF != 255
diff --git a/RELEASENOTES b/RELEASENOTES
index 3a596dd46..1fedffc8a 100644
--- a/RELEASENOTES
+++ b/RELEASENOTES
@@ -11,6 +11,8 @@ SWIG-4.1.0 summary:
 - Add PHP 8 support.
 - PHP wrapping is now done entirely via PHP's C API - no more .php wrapper.
 - Perl 5.8.0 is now the oldest version SWIG supports.
+- Common cases of `<` and `>` comparisons in constant expressions are now
+  supported.
 - GitHub Actions is now used instead of Travis CI for continuous integration.
 
 SWIG-4.0.2 summary:
diff --git a/Source/CParse/parser.y b/Source/CParse/parser.y
index 0796362bc..562c51269 100644
--- a/Source/CParse/parser.y
+++ b/Source/CParse/parser.y
@@ -1675,7 +1675,7 @@ static String *add_qualifier_to_declarator(SwigType *type, SwigType *qualifier)
 %type <type>     type rawtype type_right anon_bitfield_type decltype ;
 %type <bases>    base_list inherit raw_inherit;
 %type <dtype>    definetype def_args etype default_delete deleted_definition explicit_default;
-%type <dtype>    expr exprnum exprcompound valexpr exprmem;
+%type <dtype>    expr exprnum exprsimple exprcompound valexpr exprmem;
 %type <id>       ename ;
 %type <id>       less_valparms_greater;
 %type <str>      type_qualifier;
@@ -6533,7 +6533,8 @@ exprmem        : ID ARROW ID {
 	       }
 	       ;
 
-valexpr        : exprnum {
+/* Non-compound expression */
+exprsimple     : exprnum {
 		    $$ = $1;
                }
                | exprmem {
@@ -6553,7 +6554,6 @@ valexpr        : exprnum {
 		  $$.val = NewStringf("sizeof...(%s)",SwigType_str($6,0));
 		  $$.type = T_ULONG;
                }
-               | exprcompound { $$ = $1; }
 	       | wstring {
 		    $$.val = $1;
 		    $$.rawval = NewStringf("L\"%s\"", $$.val);
@@ -6588,6 +6588,11 @@ valexpr        : exprnum {
 		  $$.final = 0;
 	       }
 
+               ;
+
+valexpr        : exprsimple { $$ = $1; }
+	       | exprcompound { $$ = $1; }
+
 /* grouping */
                |  LPAREN expr RPAREN %prec CAST {
 		    $$.val = NewStringf("(%s)",$2.val);
@@ -6666,7 +6671,7 @@ valexpr        : exprnum {
 		 $$ = $2;
                  $$.val = NewStringf("*%s",$2.val);
 	       }
-               ;
+	       ;
 
 exprnum        :  NUM_INT { $$ = $1; }
                |  NUM_FLOAT { $$ = $1; }
@@ -6734,16 +6739,24 @@ exprcompound   : expr PLUS expr {
 		 $$.val = NewStringf("%s!=%s",COMPOUND_EXPR_VAL($1),COMPOUND_EXPR_VAL($3));
 		 $$.type = cparse_cplusplus ? T_BOOL : T_INT;
 	       }
-/* Sadly this causes 2 reduce-reduce conflicts with templates.  FIXME resolve these.
-               | expr GREATERTHAN expr {
-		 $$.val = NewStringf("%s > %s", COMPOUND_EXPR_VAL($1), COMPOUND_EXPR_VAL($3));
+	       /* Trying to parse `>` in the general case results in conflicts
+		* in the parser, but all user-reported cases are actually inside
+		* parentheses and we can handle that case.
+		*/
+	       | LPAREN expr GREATERTHAN expr RPAREN {
+		 $$.val = NewStringf("%s > %s", COMPOUND_EXPR_VAL($2), COMPOUND_EXPR_VAL($4));
 		 $$.type = cparse_cplusplus ? T_BOOL : T_INT;
 	       }
-               | expr LESSTHAN expr {
-		 $$.val = NewStringf("%s < %s", COMPOUND_EXPR_VAL($1), COMPOUND_EXPR_VAL($3));
+
+	       /* Similarly for `<` except trying to handle exprcompound on the
+		* left side gives a shift/reduce conflict, so also restrict
+		* handling to non-compound subexpressions there.  Again this
+		* covers all user-reported cases.
+		*/
+               | LPAREN exprsimple LESSTHAN expr RPAREN {
+		 $$.val = NewStringf("%s < %s", COMPOUND_EXPR_VAL($2), COMPOUND_EXPR_VAL($4));
 		 $$.type = cparse_cplusplus ? T_BOOL : T_INT;
 	       }
-*/
                | expr GREATERTHANOREQUALTO expr {
 		 $$.val = NewStringf("%s >= %s", COMPOUND_EXPR_VAL($1), COMPOUND_EXPR_VAL($3));
 		 $$.type = cparse_cplusplus ? T_BOOL : T_INT;