Support tests in freestanding

Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I'd like to make libc++ behave better with what freestanding should
be, so that it can be a tool we use in improving the standard. To do that we
need to try stuff out, both with "freestanding the language mode" and
"freestanding the library subset".

Let's start with the super basic: run the libc++ tests in freestanding, using
clang as the compiler, and see what works. The easiest hack to do this:

In utils/libcxx/test/config.py add:

  self.cxx.compile_flags += ['-ffreestanding']

Run the tests and they all fail.

Why? Because in freestanding `main` isn't special. This "not special" property
has two effects: main doesn't get mangled, and main isn't allowed to omit its
`return` statement. The first means main gets mangled and the linker can't
create a valid executable for us to test. The second means we spew out warnings
(ew) and the compiler doesn't insert the `return` we omitted, and main just
falls of the end and does whatever undefined behavior (if you're luck, ud2
leading to non-zero return code).

Let's start my work with the basics. This patch changes all libc++ tests to
declare `main` as `int main(int, char**` so it mangles consistently (enabling us
to declare another `extern "C"` main for freestanding which calls the mangled
one), and adds `return 0;` to all places where it was missing. This touches 6124
files, and I apologize.

The former was done with The Magic Of Sed.

The later was done with a (not quite correct but decent) clang tool:

  https://gist.github.com/jfbastien/793819ff360baa845483dde81170feed

This works for most tests, though I did have to adjust a few places when e.g.
the test runs with `-x c`, macros are used for main (such as for the filesystem
tests), etc.

Once this is in we can create a freestanding bot which will prevent further
regressions. After that, we can start the real work of supporting C++
freestanding fairly well in libc++.

<rdar://problem/47754795>

Reviewers: ldionne, mclow.lists, EricWF

Subscribers: christof, jkorous, dexonsmith, arphaman, miyuki, libcxx-commits

Differential Revision: https://reviews.llvm.org/D57624

llvm-svn: 353086

12 files changed, 36 insertions, 12 deletions

diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/assign.fail.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/assign.fail.cpp
index e308b20e876..a367051fec3 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/assign.fail.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/assign.fail.cpp
@@ -15,9 +15,11 @@
 #include <condition_variable>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     std::condition_variable cv0;
     std::condition_variable cv1;
     cv1 = cv0;
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/copy.fail.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/copy.fail.cpp
index d0c4c653dd3..f9d60765792 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/copy.fail.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/copy.fail.cpp
@@ -15,8 +15,10 @@
 #include <condition_variable>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     std::condition_variable cv0;
     std::condition_variable cv1(cv0);
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/default.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/default.pass.cpp
index 879d3c7dcad..aab97f9e14a 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/default.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/default.pass.cpp
@@ -17,7 +17,9 @@
 #include <condition_variable>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     std::condition_variable cv;
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/destructor.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/destructor.pass.cpp
index 85c83f92ac8..6550109fd79 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/destructor.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/destructor.pass.cpp
@@ -43,7 +43,7 @@ void g()
         cv->wait(lk);
 }
 
-int main()
+int main(int, char**)
 {
     cv = new std::condition_variable;
     std::thread th2(g);
@@ -54,4 +54,6 @@ int main()
     std::thread th1(f);
     th1.join();
     th2.join();
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_all.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_all.pass.cpp
index c281a9d2097..46c53a863f5 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_all.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_all.pass.cpp
@@ -46,7 +46,7 @@ void f2()
     test2 = 2;
 }
 
-int main()
+int main(int, char**)
 {
     std::thread t1(f1);
     std::thread t2(f2);
@@ -65,4 +65,6 @@ int main()
     t2.join();
     assert(test1 == 2);
     assert(test2 == 2);
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp
index f72d36e8abf..eb1de67db9f 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp
@@ -47,7 +47,7 @@ void f2()
     test2 = 2;
 }
 
-int main()
+int main(int, char**)
 {
     std::thread t1(f1);
     std::thread t2(f2);
@@ -95,4 +95,6 @@ int main()
     }
     else
         assert(false);
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait.pass.cpp
index a3420740641..03bcfeea94d 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait.pass.cpp
@@ -36,7 +36,7 @@ void f()
     assert(test2 != 0);
 }
 
-int main()
+int main(int, char**)
 {
     std::unique_lock<std::mutex>lk(mut);
     std::thread t(f);
@@ -48,4 +48,6 @@ int main()
     lk.unlock();
     cv.notify_one();
     t.join();
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for.pass.cpp
index f34b230c243..505997fff46 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for.pass.cpp
@@ -59,7 +59,7 @@ void f()
     ++runs;
 }
 
-int main()
+int main(int, char**)
 {
     {
         std::unique_lock<std::mutex>lk(mut);
@@ -85,4 +85,6 @@ int main()
         lk.unlock();
         t.join();
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for_pred.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for_pred.pass.cpp
index a61b000bdc9..e92ce4583c5 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for_pred.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_for_pred.pass.cpp
@@ -66,7 +66,7 @@ void f()
     ++runs;
 }
 
-int main()
+int main(int, char**)
 {
     {
         std::unique_lock<std::mutex>lk(mut);
@@ -92,4 +92,6 @@ int main()
         lk.unlock();
         t.join();
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_pred.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_pred.pass.cpp
index f99436a5e29..0de8524ed1e 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_pred.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_pred.pass.cpp
@@ -46,7 +46,7 @@ void f()
     assert(test2 != 0);
 }
 
-int main()
+int main(int, char**)
 {
     std::unique_lock<std::mutex>lk(mut);
     std::thread t(f);
@@ -58,4 +58,6 @@ int main()
     lk.unlock();
     cv.notify_one();
     t.join();
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until.pass.cpp
index f954ae25ee2..7f1bdf827cb 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until.pass.cpp
@@ -72,7 +72,7 @@ void f()
     ++runs;
 }
 
-int main()
+int main(int, char**)
 {
     {
         std::unique_lock<std::mutex>lk(mut);
@@ -98,4 +98,6 @@ int main()
         lk.unlock();
         t.join();
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until_pred.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until_pred.pass.cpp
index 8307a52c0e3..f21b1b54bc6 100644
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until_pred.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/wait_until_pred.pass.cpp
@@ -85,7 +85,7 @@ void f()
     ++runs;
 }
 
-int main()
+int main(int, char**)
 {
     {
         std::unique_lock<std::mutex>lk(mut);
@@ -111,4 +111,6 @@ int main()
         lk.unlock();
         t.join();
     }
+
+  return 0;
 }