Introduce cpp.linkerMode

This property allows qbs to automatically select an appropriate linker
based on the objects being linked. The new behavior is to automatically
use the C++ compiler driver for linking if any of the objects being
linked were compiled from C++ or Objective-C++ sources, otherwise the C
compiler driver if any of the objects being linked were compiled from C
or Objective-C sources, otherwise the system linker. To retain the old
behavior, cpp.linkerName can be set to cpp.cxxCompilerName, and
cpp.linkerMode to "manual". Qbs will also avoid passing the -stdlib
option or linking c++abi on Linux unless any of the objects being linked
were compiled from C++ or Objective-C++ sources.

As a result the default behavior for building a pure C application or
pure ASM application with Qbs is to NOT link to the C++ standard library
or any other supporting C++ libraries.

[ChangeLog] Introduced cpp.linkerMode property to allow selection of the
correct linker (C driver, C++ driver, or system linker) based on the
objects being linked

Change-Id: Ic16e31a3072c9e296c348783a21717902c15bff6
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

8 files changed, 134 insertions, 0 deletions

diff --git a/tests/auto/blackbox/testdata/linkerMode/main.c b/tests/auto/blackbox/testdata/linkerMode/main.c
new file mode 100644
index 000000000..cfc7d07f0
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/main.c
@@ -0,0 +1,8 @@
+#include <stdlib.h>
+
+int main()
+{
+    void *memory = malloc(8);
+    free(memory);
+    return 0;
+}
diff --git a/tests/auto/blackbox/testdata/linkerMode/main.cpp b/tests/auto/blackbox/testdata/linkerMode/main.cpp
new file mode 100644
index 000000000..2f360bde4
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/main.cpp
@@ -0,0 +1,8 @@
+#include <string>
+
+int main()
+{
+    std::string s = "Hello World";
+    (void)s;
+    return 0;
+}
diff --git a/tests/auto/blackbox/testdata/linkerMode/main.m b/tests/auto/blackbox/testdata/linkerMode/main.m
new file mode 100644
index 000000000..8db28e5be
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/main.m
@@ -0,0 +1,7 @@
+#include <objc/objc.h>
+
+int main()
+{
+    sel_registerName("qbs");
+    return 0;
+}
diff --git a/tests/auto/blackbox/testdata/linkerMode/main.mm b/tests/auto/blackbox/testdata/linkerMode/main.mm
new file mode 100644
index 000000000..65ef04091
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/main.mm
@@ -0,0 +1,10 @@
+#include <string>
+#include <objc/objc.h>
+
+int main()
+{
+    std::string s = "Hello World";
+    (void)s;
+    sel_registerName("qbs");
+    return 0;
+}
diff --git a/tests/auto/blackbox/testdata/linkerMode/main.s b/tests/auto/blackbox/testdata/linkerMode/main.s
new file mode 100644
index 000000000..578cc628a
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/main.s
@@ -0,0 +1,3 @@
+.global _start
+
+_start:
diff --git a/tests/auto/blackbox/testdata/linkerMode/project.qbs b/tests/auto/blackbox/testdata/linkerMode/project.qbs
new file mode 100644
index 000000000..f1cfcb52c
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/project.qbs
@@ -0,0 +1,83 @@
+import qbs
+
+Project {
+    CppApplication {
+        consoleApplication: true
+        name: "LinkedProduct-Assembly"
+        files: ["main.s"]
+
+        cpp.entryPoint: "_start"
+        cpp.dynamicLibraries: qbs.targetOS.contains("darwin") ? ["System"] : ["c"]
+
+        Group {
+            fileTagsFilter: product.type
+            qbs.install: true
+        }
+    }
+
+    CppApplication {
+        consoleApplication: true
+        name: "LinkedProduct-C"
+        files: ["main.c"]
+
+        Group {
+            fileTagsFilter: product.type
+            qbs.install: true
+        }
+    }
+
+    CppApplication {
+        condition: qbs.targetOS.contains("darwin")
+
+        consoleApplication: true
+        name: "LinkedProduct-Objective-C"
+        files: ["main.m"]
+
+        cpp.dynamicLibraries: ["ObjC"]
+
+        Group {
+            fileTagsFilter: product.type
+            qbs.install: true
+        }
+    }
+
+    CppApplication {
+        consoleApplication: true
+        name: "LinkedProduct-C++"
+        files: ["main.cpp"]
+
+        Group {
+            fileTagsFilter: product.type
+            qbs.install: true
+        }
+    }
+
+    CppApplication {
+        condition: qbs.targetOS.contains("darwin")
+
+        consoleApplication: true
+        name: "LinkedProduct-Objective-C++"
+        files: ["main.mm"]
+
+        cpp.dynamicLibraries: ["ObjC"]
+
+        Group {
+            fileTagsFilter: product.type
+            qbs.install: true
+        }
+    }
+
+    CppApplication {
+        Depends { name: "LinkedProduct-C++StaticLibrary" }
+
+        name: "LinkedProduct-BlankApp"
+        files: ["staticmain.c"]
+    }
+
+    StaticLibrary {
+        Depends { name: "cpp" }
+
+        name: "LinkedProduct-C++StaticLibrary"
+        files: ["staticlib.cpp"]
+    }
+}
diff --git a/tests/auto/blackbox/testdata/linkerMode/staticlib.cpp b/tests/auto/blackbox/testdata/linkerMode/staticlib.cpp
new file mode 100644
index 000000000..663658d88
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/staticlib.cpp
@@ -0,0 +1,9 @@
+#include <iostream>
+
+extern "C" int cpp();
+
+int cpp()
+{
+    std::cout << "Hello world" << std::endl;
+    return 0;
+}
diff --git a/tests/auto/blackbox/testdata/linkerMode/staticmain.c b/tests/auto/blackbox/testdata/linkerMode/staticmain.c
new file mode 100644
index 000000000..763f9e388
--- /dev/null
+++ b/tests/auto/blackbox/testdata/linkerMode/staticmain.c
@@ -0,0 +1,6 @@
+extern int cpp();
+
+int main()
+{
+    return cpp();
+}