C++ linker presentation

cpplinker/08_lto/build.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+set -e
+
+echo "=== Build WITHOUT LTO ==="
+g++ -std=c++17 -O2 -c foo.cpp  -o foo.o
+g++ -std=c++17 -O2 -c main.cpp -o main.o
+g++ -O2 foo.o main.o -o app_nolto -lm
+echo "Created app_nolto"
+
+echo ""
+echo "=== Build WITH LTO ==="
+g++ -std=c++17 -O2 -flto -c foo.cpp  -o foo_lto.o
+g++ -std=c++17 -O2 -flto -c main.cpp -o main_lto.o
+g++ -O2 -flto foo_lto.o main_lto.o -o app_lto -lm
+echo "Created app_lto"
+
+echo ""
+echo "=== Compare binary sizes ==="
+ls -l app_nolto app_lto
+
+echo ""
+echo "=== Run both ==="
+echo -n "no-lto: "; ./app_nolto
+echo -n "lto:    "; ./app_lto

cpplinker/08_lto/foo.cpp

@@ -0,0 +1,9 @@
+#include <cmath>
+
+double heavy_compute(double x) {
+    double result = 0;
+    for (int i = 0; i < 1000; i++) {
+        result += std::sin(x + i) * std::cos(x - i);
+    }
+    return result;
+}

cpplinker/08_lto/main.cpp

@@ -0,0 +1,9 @@
+#include <iostream>
+
+double heavy_compute(double);
+
+int main() {
+    double r = heavy_compute(1.0);
+    std::cout << "result = " << r << "\n";
+    return 0;
+}