diff --git a/xo-expression/example/ex1/ex1.cpp b/xo-expression/example/ex1/ex1.cpp
index 5dd91fe2..0c69cab4 100644
--- a/xo-expression/example/ex1/ex1.cpp
+++ b/xo-expression/example/ex1/ex1.cpp
@@ -5,6 +5,14 @@
 #include "xo/expression/llvmintrinsic.hpp"
 #include <iostream>
 #include <cmath>
+#include <math.h>
+
+// address of &sqrt ambiguous on osx/clang
+// (perhaps it's a template..?)
+//
+double xo_sqrt(double x) {
+    return sqrt(x);
+}
 
 int
 main() {
@@ -20,7 +28,7 @@ main() {
 
     {
         auto expr = make_primitive("sqrt",
-                                   &::sqrt,
+                                   &xo_sqrt,
                                    false /*!explicit_symbol_def*/,
                                    llvmintrinsic::fp_sqrt);
 
diff --git a/xo-jit/example/ex1/ex1.cpp b/xo-jit/example/ex1/ex1.cpp
index 22e1b0b7..638e1bda 100644
--- a/xo-jit/example/ex1/ex1.cpp
+++ b/xo-jit/example/ex1/ex1.cpp
@@ -29,8 +29,28 @@
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar/Reassociate.h"
 #include "llvm/Transforms/Scalar/SimplifyCFG.h"
+#include <cmath>
 
-//double foo(double x) { return x; }
+namespace {
+    // need wrappers to fix type signature for osx/clang15.  Perhaps sqrt() is a macro or template (?)
+    double
+    xo_sqrt(double x)
+    {
+        return ::sqrt(x);
+    }
+
+    double
+    xo_sin(double x)
+    {
+        return ::sin(x);
+    }
+
+    double
+    xo_cos(double x)
+    {
+        return ::cos(x);
+    }
+}
 
 int
 main() {
@@ -82,7 +102,7 @@ main() {
     }
 
     {
-        auto expr = make_primitive("sqrt", &sqrt,
+        auto expr = make_primitive("sqrt", &xo_sqrt,
                                    false /*!explicit_symbol_def*/,
                                    llvmintrinsic::fp_sqrt);
 
@@ -105,7 +125,7 @@ main() {
     {
         /* (sqrt 2) */
 
-        auto fn = make_primitive("sqrt", &sqrt,
+        auto fn = make_primitive("sqrt", &xo_sqrt,
                                  false /*!explicit_symbol_def*/,
                                  llvmintrinsic::fp_sqrt);
         auto arg = make_constant(2.0);
@@ -132,11 +152,11 @@ main() {
         /* (lambda (x) (sin (cos x))) */
 
         auto sin = make_primitive("sin",
-                                  ::sin,
+                                  &xo_sin,
                                   false /*!explicit_symbol_def*/,
                                   llvmintrinsic::fp_sin);
         auto cos = make_primitive("cos",
-                                  ::cos,
+                                  &xo_cos,
                                   false /*!explicit_symbol_def*/,
                                   llvmintrinsic::fp_cos);
 
diff --git a/xo-jit/example/ex2_jit/ex2_jit.cpp b/xo-jit/example/ex2_jit/ex2_jit.cpp
index 3131f823..b21d5e41 100644
--- a/xo-jit/example/ex2_jit/ex2_jit.cpp
+++ b/xo-jit/example/ex2_jit/ex2_jit.cpp
@@ -33,6 +33,15 @@
 
 //double foo(double x) { return x; }
 
+namespace {
+    // need wrappers to pin type signature for osx/clang15
+    double
+    xo_sqrt(double x)
+    {
+        return ::sqrt(x);
+    }
+}
+
 int
 main() {
     using xo::scope;
@@ -68,7 +77,7 @@ main() {
 
     {
         auto sqrt = make_primitive("sqrt",
-                                   ::sqrt,
+                                   &xo_sqrt,
                                    false /*!explicit_symbol_def*/,
                                    llvmintrinsic::fp_sqrt);
 
@@ -115,7 +124,7 @@ main() {
 #elif CHOICE == 2
 #define FUNCTION_SYMBOL "twice"
         auto root = make_primitive("sqrt",
-                                   ::sqrt,
+                                   &xo_sqrt,
                                    false /*!explicit_symbol_def*/,
                                    llvmintrinsic::fp_sqrt);
 
diff --git a/xo-reader/src/reader/exprseq_xs.cpp b/xo-reader/src/reader/exprseq_xs.cpp
index b934c2ef..421b037c 100644
--- a/xo-reader/src/reader/exprseq_xs.cpp
+++ b/xo-reader/src/reader/exprseq_xs.cpp
@@ -66,8 +66,6 @@ namespace xo {
         {
             /* toplevel expression sequence accepts an
              * arbitrary number of expressions.
-             *
-             * parser::include_token() returns
              */
 
             auto p_emit_expr = p_psm->p_emit_expr_;
diff --git a/xo-unit/include/xo/unit/dimension.hpp b/xo-unit/include/xo/unit/dimension.hpp
index c28936e2..c926455b 100644
--- a/xo-unit/include/xo/unit/dimension.hpp
+++ b/xo-unit/include/xo/unit/dimension.hpp
@@ -2,6 +2,9 @@
 
 #pragma once
 
+#ifdef __APPL__
+# include <vector>  // for std::size_t when building with clang18
+#endif
 #include <cstdint>
 
 namespace xo {
@@ -58,7 +61,7 @@ namespace xo {
         }
 
         /** @brief number of built-in dimensions, convenient for array sizing **/
-        static constexpr std::size_t n_dim = static_cast<std::size_t>(dimension::n_dim);
+        static constexpr std::uint64_t n_dim = static_cast<std::uint64_t>(dimension::n_dim);
     } /*namespace qty*/
 } /*namespace xo*/