C++ linker presentation

cpplinker/06_c_interop/build.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+set -e
+
+echo "=== Compile C++ wrapper ==="
+g++ -std=c++17 -c wrapper.cpp -o wrapper.o
+
+echo ""
+echo "=== Compile C main ==="
+gcc -std=c11 -c main.c -o main.o
+
+echo ""
+echo "=== Symbols in wrapper.o (note: unmangled due to extern C) ==="
+nm -g wrapper.o | grep vec_
+
+echo ""
+echo "=== Symbols in main.o (C code references) ==="
+nm -u main.o | grep vec_
+
+echo ""
+echo "=== Link (use g++ to pull in C++ runtime) ==="
+g++ wrapper.o main.o -o app
+echo "Created app"
+
+echo ""
+echo "=== Run ==="
+./app

cpplinker/06_c_interop/main.c

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+#include <stdio.h>
+#include "wrapper.h"
+
+int main(void) {
+    void* vec;
+    vec_create(&vec);
+
+    vec_push(vec, 3.14);
+    vec_push(vec, 2.71);
+    vec_push(vec, 1.41);
+
+    printf("vector size: %d\n", vec_size(vec));
+    for (int i = 0; i < vec_size(vec); i++) {
+        printf("  [%d] = %.2f\n", i, vec_get(vec, i));
+    }
+
+    vec_destroy(vec);
+    return 0;
+}

cpplinker/06_c_interop/wrapper.cpp

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+#include "wrapper.h"
+#include <vector>
+
+extern "C" {
+void vec_create(void** out) {
+    *out = new std::vector<double>();
+}
+
+void vec_destroy(void* vec) {
+    delete static_cast<std::vector<double>*>(vec);
+}
+
+void vec_push(void* vec, double val) {
+    static_cast<std::vector<double>*>(vec)->push_back(val);
+}
+
+double vec_get(void* vec, int idx) {
+    return (*static_cast<std::vector<double>*>(vec))[idx];
+}
+
+int vec_size(void* vec) {
+    return static_cast<std::vector<double>*>(vec)->size();
+}
+}

cpplinker/06_c_interop/wrapper.h

@@ -0,0 +1,12 @@
+#pragma once
+#ifdef __cplusplus
+extern "C" {
+#endif
+    void   vec_create(void** out);
+    void   vec_destroy(void* vec);
+    void   vec_push(void* vec, double val);
+    double vec_get(void* vec, int idx);
+    int    vec_size(void* vec);
+#ifdef __cplusplus
+}
+#endif