C++ linker presentation

cpplinker/05_dynamic_linking/build.sh

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+#!/bin/bash
+set -e
+
+echo "=== Compile with -fPIC for position-independent code ==="
+g++ -std=c++17 -fPIC -c vec.cpp -o vec.o
+g++ -std=c++17 -fPIC -c mat.cpp -o mat.o
+
+echo ""
+echo "=== Create shared library ==="
+g++ -shared vec.o mat.o -o libmymath.so
+echo "Created libmymath.so"
+
+echo ""
+echo "=== Symbols exported by the shared library ==="
+nm -C -D libmymath.so | grep -E "vec_|mat_"
+
+echo ""
+echo "=== Compile and link main dynamically ==="
+g++ -std=c++17 -c main.cpp -o main.o
+g++ main.o -L. -lmymath -Wl,-rpath,'$ORIGIN' -o app
+echo "Created app"
+
+echo ""
+echo "=== Runtime dependencies ==="
+ldd app
+
+echo ""
+echo "=== Run ==="
+./app

cpplinker/05_dynamic_linking/main.cpp

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+#include <iostream>
+
+void vec_add(double[3], double[3], double[3]);
+void vec_print(double[3]);
+void mat_identity(double[9]);
+void mat_print(double[9]);
+
+int main() {
+    double a[3] = {1, 2, 3};
+    double b[3] = {4, 5, 6};
+    double c[3];
+
+    vec_add(a, b, c);
+    std::cout << "vec_add: ";
+    vec_print(c);
+
+    double m[9];
+    mat_identity(m);
+    std::cout << "identity matrix:\n";
+    mat_print(m);
+
+    return 0;
+}

cpplinker/05_dynamic_linking/mat.cpp

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+#include <iostream>
+
+void mat_identity(double m[9]) {
+    for (int i = 0; i < 9; i++) m[i] = 0.0;
+    m[0] = m[4] = m[8] = 1.0;
+}
+
+void mat_print(double m[9]) {
+    for (int r = 0; r < 3; r++) {
+        std::cout << "| " << m[r*3] << " " << m[r*3+1] << " " << m[r*3+2] << " |\n";
+    }
+}

cpplinker/05_dynamic_linking/vec.cpp

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+#include <iostream>
+
+void vec_add(double a[3], double b[3], double out[3]) {
+    for (int i = 0; i < 3; i++) out[i] = a[i] + b[i];
+}
+
+void vec_print(double v[3]) {
+    std::cout << "(" << v[0] << ", " << v[1] << ", " << v[2] << ")\n";
+}