From 7b00705bc32ab3b7b00a9fca65c6f8403507dac1 Mon Sep 17 00:00:00 2001
From: Aaron Jomy <aaronjomyjoseph@gmail.com>
Date: Fri, 28 Aug 2026 17:58:05 +0200
Subject: [PATCH] [cpyrt] Add CStringArrayConverter::ToMemory

Assigning to a const char** data member inherited the buffer-only
ToMemory of the base converter, so a Python string was rejected with a
property type mismatch. Accept a string as well, with the buffer copy
factored into a helper covering the fixed and unbounded cases and the
lifetime tie-in.
---
 src/cpyrt/Converters.cxx      | 46 +++++++++++++++++++++++++++++++++++
 src/cpyrt/DeclareConverters.h |  1 +
 test/test_lowlevel.py         | 19 +++++++++++++++
 3 files changed, 66 insertions(+)

diff --git a/src/cpyrt/Converters.cxx b/src/cpyrt/Converters.cxx
index 4771e80..8e1e7ec 100644
--- a/src/cpyrt/Converters.cxx
+++ b/src/cpyrt/Converters.cxx
@@ -1710,6 +1710,41 @@ bool cpyrt::StdSpanConverter::SetArg(PyObject* pyobject, Parameter& para,
 
 #endif // __cplusplus >= 202002L
 
+namespace {
+
+template <class type>
+bool ToArrayFromBuffer(PyObject* owner, void* address, PyObject* ctxt,
+                       const void* buf, Py_ssize_t buflen, cpyrt::dims_t& shape,
+                       bool isFixed) {
+  if (buflen == 0)
+    return false;
+
+  Py_ssize_t oldsz = 1;
+  for (Py_ssize_t idim = 0; idim < shape.ndim(); ++idim) {
+    if (shape[idim] == cpyrt::UNKNOWN_SIZE) {
+      oldsz = -1;
+      break;
+    }
+    oldsz *= shape[idim];
+  }
+  if (shape.ndim() != cpyrt::UNKNOWN_SIZE && 0 < oldsz && oldsz < buflen) {
+    PyErr_SetString(PyExc_ValueError, "buffer too large for value");
+    return false;
+  }
+
+  if (isFixed)
+    memcpy(*(type**)address, buf, (0 < buflen ? buflen : 1) * sizeof(type));
+  else {
+    *(type**)address = (type*)buf;
+    shape.ndim(1);
+    shape[0] = buflen;
+    SetLifeLine(ctxt, owner, (intptr_t)address);
+  }
+  return true;
+}
+
+} // namespace
+
 //----------------------------------------------------------------------------
 #define CPPJIT_IMPL_ARRAY_CONVERTER(name, ctype, type, code, suffix)           \
   cpyrt::name##ArrayConverter::name##ArrayConverter(cdims_t dims)              \
@@ -1917,6 +1952,17 @@ PyObject* cpyrt::CStringArrayConverter::FromMemory(void* address) {
   return CreateLowLevelViewString(*(const char***)address, fShape);
 }
 
+bool cpyrt::CStringArrayConverter::ToMemory(PyObject* value, void* address,
+                                            PyObject* ctxt) {
+  // Unlike the other array converters, this one also accepts a Python string.
+  Py_ssize_t len;
+  if (const char* cstr = cpyrt_PyText_AsStringAndSize(value, &len)) {
+    return ToArrayFromBuffer<char>(value, address, ctxt, cstr, len, fShape,
+                                   fIsFixed);
+  }
+  return SCharArrayConverter::ToMemory(value, address, ctxt);
+}
+
 //----------------------------------------------------------------------------
 PyObject* cpyrt::NonConstCStringArrayConverter::FromMemory(void* address) {
   if (fIsFixed)
diff --git a/src/cpyrt/DeclareConverters.h b/src/cpyrt/DeclareConverters.h
index efbf797..3347e18 100644
--- a/src/cpyrt/DeclareConverters.h
+++ b/src/cpyrt/DeclareConverters.h
@@ -249,6 +249,7 @@ class CStringArrayConverter : public SCharArrayConverter {
   using SCharArrayConverter::SCharArrayConverter;
   bool SetArg(PyObject*, Parameter&, CallContext* = nullptr) override;
   PyObject* FromMemory(void* address) override;
+  bool ToMemory(PyObject*, void*, PyObject* = nullptr) override;
   std::string GetFailureMsg() override { return "[CStringArrayConverter]"; };
 
 private:
diff --git a/test/test_lowlevel.py b/test/test_lowlevel.py
index 8bb395e..b6ad122 100644
--- a/test/test_lowlevel.py
+++ b/test/test_lowlevel.py
@@ -1159,3 +1159,22 @@ def test08_reshape_sets_unknown_dimensions_only(self):
         # a freshly constructed view has no dimensions to set
         v = cppjit._backend.LowLevelView()
         raises(TypeError, v.reshape, ())
+
+
+class TestCSTRINGARRAY:
+    def test01_cstring_array_from_str(self):
+        """A Python string can be assigned to a const char** data member"""
+
+        import cppjit
+
+        cppjit.cppdef("""\
+        namespace CStringArray {
+            struct S { const char** names = nullptr; };
+            const char* as_chars(S& s) { return (const char*)s.names; }
+        }""")
+
+        ns = cppjit.gbl.CStringArray
+        s = ns.S()
+
+        s.names = "abc"
+        assert ns.as_chars(s) == "abc"