[c-api] Generate C wrappers from TableGen instead of hand-writing them. by vgvassilev · Pull Request #921 · compiler-research/CppInterOp

vgvassilev · 2026-04-24T14:03:49Z

The old clang-c/CXCppInterOp.h and CXCppInterOp.cpp maintained ~470 lines of hand-written C forwarding code that drifted from the C++ API on every change. CTypeMap records in CppInterOpAPI.td now drive the emitter to produce CXCppInterOpDecl.inc (C-compatible declarations) and CXCppInterOpImpl.inc (C++ implementations) as two separate files with no preprocessor guards needed at include sites.

CTypeMap supports scalar passthrough, opaque pointer erasure, string and enum conversions, and collection signature rewriting (vector returns, out-params, in-params, string collections). CppInterOpArray, CppInterOpStringArray, and TemplateArgInfo use typedef struct for C compatibility, living at file scope in C and inside namespace CppImpl in C++. Functions the emitter cannot handle mechanically (GetClassTemplatedMethods, MakeFunctionCallable, GetDimensions) are marked NoCWrapper; GetClassTemplatedMethods has a hand-written wrapper in CXCppInterOp.cpp.

Adds CAPITestC.c (pure C compilation of all declarations), C API dispatch tests via dlsym, and focused tests for scalars, enums, collections, and vector in-params.

codecov · 2026-04-24T14:19:51Z

Codecov Report

❌ Patch coverage is 95.67100% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.89%. Comparing base (c49ea8e) to head (9c32d55).
⚠️ Report is 54 commits behind head on main.

Files with missing lines	Patch %	Lines
utils/TableGen/CppInterOpEmitter.cpp	95.34%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #921      +/-   ##
==========================================
+ Coverage   83.02%   85.89%   +2.87%     
==========================================
  Files          15       15              
  Lines        5079     4971     -108     
==========================================
+ Hits         4217     4270      +53     
+ Misses        862      701     -161

Files with missing lines	Coverage Δ
include/CppInterOp/CppInterOpTypes.h	`93.87% <100.00%> (ø)`
lib/CppInterOp/CXCppInterOp.cpp	`100.00% <100.00%> (+49.71%)`	⬆️
utils/TableGen/TableGen.cpp	`100.00% <100.00%> (ø)`
utils/TableGen/CppInterOpEmitter.cpp	`96.76% <95.34%> (-3.24%)`	⬇️

... and 4 files with indirect coverage changes

Files with missing lines	Coverage Δ
include/CppInterOp/CppInterOpTypes.h	`93.87% <100.00%> (ø)`
lib/CppInterOp/CXCppInterOp.cpp	`100.00% <100.00%> (+49.71%)`	⬆️
utils/TableGen/TableGen.cpp	`100.00% <100.00%> (ø)`
utils/TableGen/CppInterOpEmitter.cpp	`96.76% <95.34%> (-3.24%)`	⬇️

... and 4 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

github-actions

clang-tidy made some suggestions

There were too many comments to post at once. Showing the first 10 out of 46. Check the log or trigger a new build to see more.

github-actions · 2026-04-24T15:38:29Z


+// C-compatible headers — usable from both C and C++.
+#include <stdbool.h>
+#include <stddef.h>


warning: including 'stdbool.h' has no effect in C++; consider removing it [modernize-deprecated-headers]

Suggested change

#include <stddef.h>

.

github-actions · 2026-04-24T15:38:29Z

+// C-compatible headers — usable from both C and C++.
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>


warning: inclusion of deprecated C++ header 'stddef.h'; consider using 'cstddef' instead [modernize-deprecated-headers]

Suggested change

#include <stdint.h>

>

><cstddef>

github-actions · 2026-04-24T15:38:29Z

+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus


warning: inclusion of deprecated C++ header 'stdint.h'; consider using 'cstdint' instead [modernize-deprecated-headers]

Suggested change

#ifdef __cplusplus

>

><cstdint>

github-actions · 2026-04-24T15:38:29Z

+#include <cstddef>
+#include <cstdint>
+#include <set>
+#include <string>


warning: included header set is not used directly [misc-include-cleaner]

Suggested change

#include <string>

>

github-actions · 2026-04-24T15:38:29Z

+#include <cstdint>
+#include <set>
+#include <string>
+#include <vector>


warning: included header string is not used directly [misc-include-cleaner]

Suggested change

#include <vector>

>

github-actions · 2026-04-24T15:38:29Z

+#include <string>
+#include <vector>
+
 namespace CppImpl {


warning: included header vector is not used directly [misc-include-cleaner]

Suggested change

namespace CppImpl {

>

github-actions · 2026-04-24T15:38:29Z

+  void** data;
+  size_t size;
+} CppInterOpArray;
+


warning: use 'using' instead of 'typedef' [modernize-use-using]

Suggested change

.

using CppInterOpArray = struct CppInterOpArray {

void** data;

size_t size;

}

github-actions · 2026-04-24T15:38:30Z

+  char** data;
+  size_t size;
+} CppInterOpStringArray;
+


warning: use 'using' instead of 'typedef' [modernize-use-using]

Suggested change

.

using CppInterOpStringArray = struct CppInterOpStringArray {

char** data;

size_t size;

}

github-actions · 2026-04-24T15:38:30Z

+      : m_Type(type), m_IntegralValue(integral_value) {}
+#endif
+} TemplateArgInfo;
+


warning: use 'using' instead of 'typedef' [modernize-use-using]

Suggested change

.

using TemplateArgInfo = struct TemplateArgInfo {

void* m_Type;

const char* m_IntegralValue;

#ifdef __cplusplus

TemplateArgInfo(void* type, const char* integral_value = nullptr)

: m_Type(type), m_IntegralValue(integral_value) {}

#endif

}

github-actions · 2026-04-24T15:38:30Z

-    return clang::cxscope::MakeCXScope(CXXRD->getDestructor(), getNewTU(S));
+// GetClassTemplatedMethods returns bool AND fills a vector out-param.
+// The C wrapper drops the bool (caller checks arr.size > 0 instead).
+CPPINTEROP_API Cpp::CppInterOpArray


warning: no header providing "CPPINTEROP_API" is directly included [misc-include-cleaner]

CPPINTEROP_API Cpp::CppInterOpArray ^

github-actions

clang-tidy made some suggestions

There were too many comments to post at once. Showing the first 10 out of 36. Check the log or trigger a new build to see more.

github-actions · 2026-04-24T16:45:28Z

-    return clang::cxscope::MakeCXScope(CXXRD->getDestructor(), getNewTU(S));
+// GetClassTemplatedMethods returns bool AND fills a vector out-param.
+// The C wrapper drops the bool (caller checks arr.size > 0 instead).
+CPPINTEROP_API Cpp::CppInterOpArray


warning: no header providing "CppImpl::CppInterOpArray" is directly included [misc-include-cleaner]

lib/CppInterOp/CXCppInterOp.cpp:6:

- #include <cstdlib> + #include <CppInterOp/CppInterOpTypes.h> + #include <cstdlib>

github-actions · 2026-04-24T16:45:28Z

+// The C wrapper drops the bool (caller checks arr.size > 0 instead).
+CPPINTEROP_API Cpp::CppInterOpArray
+cppinterop_GetClassTemplatedMethods(const char* name, void* parent) {
+  std::vector<Cpp::TCppFunction_t> out;


warning: no header providing "CppImpl::TCppFunction_t" is directly included [misc-include-cleaner]

std::vector<Cpp::TCppFunction_t> out; ^

github-actions · 2026-04-24T16:45:28Z

+CPPINTEROP_API Cpp::CppInterOpArray
+cppinterop_GetClassTemplatedMethods(const char* name, void* parent) {
+  std::vector<Cpp::TCppFunction_t> out;
+  Cpp::GetClassTemplatedMethods(std::string(name), parent, out);


warning: no header providing "std::string" is directly included [misc-include-cleaner]

lib/CppInterOp/CXCppInterOp.cpp:8:

- #include <vector> + #include <string> + #include <vector>

github-actions · 2026-04-24T16:45:28Z

+  Cpp::GetClassTemplatedMethods(std::string(name), parent, out);
+  Cpp::CppInterOpArray arr = {nullptr, out.size()};
+  if (arr.size) {
+    arr.data = static_cast<void**>(malloc(arr.size * sizeof(void*)));


warning: assigning newly created 'gsl::owner<>' to non-owner 'void **' [cppcoreguidelines-owning-memory]

arr.data = static_cast<void**>(malloc(arr.size * sizeof(void*))); ^

github-actions · 2026-04-24T16:45:28Z

+  Cpp::GetClassTemplatedMethods(std::string(name), parent, out);
+  Cpp::CppInterOpArray arr = {nullptr, out.size()};
+  if (arr.size) {
+    arr.data = static_cast<void**>(malloc(arr.size * sizeof(void*)));


warning: do not manage memory manually; consider a container or a smart pointer [cppcoreguidelines-no-malloc]

arr.data = static_cast<void**>(malloc(arr.size * sizeof(void*))); ^

github-actions · 2026-04-24T16:45:29Z

+  Cpp::CppInterOpArray arr = {nullptr, out.size()};
+  if (arr.size) {
+    arr.data = static_cast<void**>(malloc(arr.size * sizeof(void*)));
+    memcpy(arr.data, out.data(), arr.size * sizeof(void*));


warning: multilevel pointer conversion from 'void **' to 'const void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]

memcpy(arr.data, out.data(), arr.size * sizeof(void*)); ^

github-actions · 2026-04-24T16:45:29Z

+  Cpp::CppInterOpArray arr = {nullptr, out.size()};
+  if (arr.size) {
+    arr.data = static_cast<void**>(malloc(arr.size * sizeof(void*)));
+    memcpy(arr.data, out.data(), arr.size * sizeof(void*));


warning: multilevel pointer conversion from 'void **' to 'void *', please use explicit cast [bugprone-multi-level-implicit-pointer-conversion]

memcpy(arr.data, out.data(), arr.size * sizeof(void*)); ^

github-actions · 2026-04-24T16:45:29Z

+#include <cstdlib>
+#include <cstring>
+
+using Cpp::CppInterOpArray;


warning: no header providing "CppImpl::CppInterOpArray" is directly included [misc-include-cleaner]

lib/CppInterOp/CXCppInterOpGenerated.cpp:5:

- #include <cstdlib> + #include <CppInterOp/CppInterOpTypes.h> + #include <cstdlib>

github-actions · 2026-04-24T16:45:29Z

+#include <cstring>
+
+using Cpp::CppInterOpArray;
+using Cpp::CppInterOpStringArray;


warning: no header providing "CppImpl::CppInterOpStringArray" is directly included [misc-include-cleaner]

using Cpp::CppInterOpStringArray; ^

github-actions · 2026-04-24T16:45:29Z

+
+using Cpp::CppInterOpArray;
+using Cpp::CppInterOpStringArray;
+using Cpp::TemplateArgInfo;


warning: no header providing "CppImpl::TemplateArgInfo" is directly included [misc-include-cleaner]

using Cpp::TemplateArgInfo; ^

github-actions

clang-tidy made some suggestions

There were too many comments to post at once. Showing the first 10 out of 26. Check the log or trigger a new build to see more.

github-actions · 2026-04-26T07:26:33Z

+#include "CppInterOp/CXCppInterOpDecl.inc"
+
+// Hand-written wrappers not in the .inc file.
+CPPINTEROP_API Cpp::CppInterOpArray


warning: no header providing "CPPINTEROP_API" is directly included [misc-include-cleaner]

CPPINTEROP_API Cpp::CppInterOpArray ^

github-actions · 2026-04-26T07:26:33Z

+#include "CppInterOp/CXCppInterOpDecl.inc"
+
+// Hand-written wrappers not in the .inc file.
+CPPINTEROP_API Cpp::CppInterOpArray


warning: no header providing "CppImpl::CppInterOpArray" is directly included [misc-include-cleaner]

unittests/CppInterOp/CAPITest.cpp:7:

- #include <cstdlib> + #include <CppInterOp/CppInterOpTypes.h> + #include <cstdlib>

github-actions · 2026-04-26T07:26:33Z

+TYPED_TEST(CppInterOpTest, CAPI_Construct) {
+  if (TypeParam::isOutOfProcess)
+    GTEST_SKIP() << "Test fails for OOP JIT builds";
+  std::vector<const char*> args = {"-include", "new"};


warning: no header providing "std::vector" is directly included [misc-include-cleaner]

unittests/CppInterOp/CAPITest.cpp:9:

+ #include <vector>

github-actions · 2026-04-26T07:26:33Z

+  Cpp::Declare("namespace CAPIStrNs { enum E1 { P, Q }; enum E2 { R }; }");
+
+  auto* ns = cppinterop_GetNamed("CAPIStrNs", nullptr);
+  Cpp::CppInterOpStringArray enums = cppinterop_GetEnums(ns);


warning: no header providing "CppImpl::CppInterOpStringArray" is directly included [misc-include-cleaner]

Cpp::CppInterOpStringArray enums = cppinterop_GetEnums(ns); ^

github-actions · 2026-04-26T07:26:33Z

+  Cpp::CppInterOpStringArray enums = cppinterop_GetEnums(ns);
+  EXPECT_EQ(enums.size, 2U);
+  // Verify the enum names are present (order may vary).
+  bool foundE1 = false, foundE2 = false;


warning: multiple declarations in a single statement reduces readability [readability-isolate-declaration]

Suggested change

bool foundE1 = false, foundE2 = false;

bool foundE1 = false;

bool foundE2 = false;

github-actions · 2026-04-26T07:26:34Z

+
+TYPED_TEST(CppInterOpTest, CAPI_CreateInterpreterInParam) {
+  // Test the vector in-param pattern: CreateInterpreter(ptr, size, ptr, size).
+  const char* args[] = {"-std=c++17"};


warning: do not declare C-style arrays, use std::array<> instead [cppcoreguidelines-avoid-c-arrays]

const char* args[] = {"-std=c++17"}; ^

github-actions · 2026-04-26T07:26:34Z

+TYPED_TEST(CppInterOpTest, CAPI_CreateInterpreterInParam) {
+  // Test the vector in-param pattern: CreateInterpreter(ptr, size, ptr, size).
+  const char* args[] = {"-std=c++17"};
+  auto* I = cppinterop_CreateInterpreter(args, 1, nullptr, 0);


warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]

auto* I = cppinterop_CreateInterpreter(args, 1, nullptr, 0); ^

github-actions · 2026-04-26T07:26:34Z

+
+namespace {
+/// RAII wrapper for a dlopen handle used by the C API dispatch tests.
+class DlHandle {


warning: class 'DlHandle' defines a non-default destructor, a copy constructor and a copy assignment operator but does not define a move constructor or a move assignment operator [cppcoreguidelines-special-member-functions]

. ^

github-actions · 2026-04-26T07:26:34Z

+  DlHandle& operator=(const DlHandle&) = delete;
+  explicit DlHandle(const char* path) {
+#ifndef _WIN32
+    H = dlopen(path, RTLD_LOCAL | RTLD_NOW);


warning: no header providing "RTLD_LOCAL" is directly included [misc-include-cleaner]

2 ^

github-actions · 2026-04-26T07:26:34Z

+  DlHandle& operator=(const DlHandle&) = delete;
+  explicit DlHandle(const char* path) {
+#ifndef _WIN32
+    H = dlopen(path, RTLD_LOCAL | RTLD_NOW);


warning: no header providing "RTLD_NOW" is directly included [misc-include-cleaner]

2 ^

The old clang-c/CXCppInterOp.h and CXCppInterOp.cpp maintained ~470 lines of hand-written C forwarding code that drifted from the C++ API on every change. CTypeMap records in CppInterOpAPI.td now drive the emitter to produce CXCppInterOpDecl.inc (C-compatible declarations) and CXCppInterOpImpl.inc (C++ implementations) as two separate files with no preprocessor guards needed at include sites. CTypeMap supports scalar passthrough, opaque pointer erasure, string and enum conversions, and collection signature rewriting (vector returns, out-params, in-params, string collections). CppInterOpArray, CppInterOpStringArray, and TemplateArgInfo use typedef struct for C compatibility, living at file scope in C and inside namespace CppImpl in C++. Functions the emitter cannot handle mechanically (GetClassTemplatedMethods, MakeFunctionCallable, GetDimensions) are marked NoCWrapper; GetClassTemplatedMethods has a hand-written wrapper in CXCppInterOp.cpp. Adds CAPITestC.c (pure C compilation of all declarations), C API dispatch tests via dlsym, and focused tests for scalars, enums, collections, and vector in-params.

vgvassilev requested review from Vipul-Cariappa and aaronj0 April 24, 2026 14:03

vgvassilev force-pushed the c-layer-rework branch from fe01513 to f2d0aa4 Compare April 24, 2026 14:15

vgvassilev force-pushed the c-layer-rework branch 3 times, most recently from fb435c4 to d7a9760 Compare April 24, 2026 15:14

github-actions Bot reviewed Apr 24, 2026

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vgvassilev force-pushed the c-layer-rework branch 2 times, most recently from 5215f6b to 8ec7eba Compare April 24, 2026 16:20

github-actions Bot reviewed Apr 24, 2026

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vgvassilev mentioned this pull request Apr 25, 2026

Move CXCppInterOp.h to CppInterOp folder #935

Closed

vgvassilev force-pushed the c-layer-rework branch from 8ec7eba to fc336e4 Compare April 26, 2026 06:54

github-actions Bot reviewed Apr 26, 2026

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vgvassilev force-pushed the c-layer-rework branch from fc336e4 to 81fd66e Compare May 2, 2026 15:15

vgvassilev force-pushed the c-layer-rework branch 3 times, most recently from 7a5e50f to bf639b0 Compare May 13, 2026 14:57

vgvassilev force-pushed the c-layer-rework branch from bf639b0 to 9c32d55 Compare May 13, 2026 16:10

vgvassilev merged commit 5197645 into compiler-research:main May 13, 2026
26 checks passed

vgvassilev deleted the c-layer-rework branch May 13, 2026 18:26

+.
+using TemplateArgInfo = struct TemplateArgInfo {
+  void* m_Type;
+  const char* m_IntegralValue;
+#ifdef __cplusplus
+  TemplateArgInfo(void* type, const char* integral_value = nullptr)
+      : m_Type(type), m_IntegralValue(integral_value) {}
+#endif
+}

	bool foundE1 = false, foundE2 = false;
	bool foundE1 = false;
	bool foundE2 = false;

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