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

10 files changed, 36 insertions, 16 deletions

diff --git a/libcxx/test/std/strings/basic.string/string.access/at.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/at.pass.cpp
index 6515e272721..514d1a894ce 100644
--- a/libcxx/test/std/strings/basic.string/string.access/at.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/at.pass.cpp
@@ -54,7 +54,7 @@ test(S s, typename S::size_type pos)
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -74,4 +74,6 @@ int main()
     test(S("123"), 3);
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.access/back.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/back.pass.cpp
index b4108010ac3..3831da0845c 100644
--- a/libcxx/test/std/strings/basic.string/string.access/back.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/back.pass.cpp
@@ -31,7 +31,7 @@ test(S s)
     assert(s.back() == typename S::value_type('z'));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -52,4 +52,6 @@ int main()
         assert(false);
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.access/db_back.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/db_back.pass.cpp
index 5034bfa11a9..e1cf707a6f0 100644
--- a/libcxx/test/std/strings/basic.string/string.access/db_back.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/db_back.pass.cpp
@@ -22,7 +22,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -46,8 +46,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/std/strings/basic.string/string.access/db_cback.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/db_cback.pass.cpp
index ddffb6cd787..e3e6db525e4 100644
--- a/libcxx/test/std/strings/basic.string/string.access/db_cback.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/db_cback.pass.cpp
@@ -22,7 +22,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -42,8 +42,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/std/strings/basic.string/string.access/db_cfront.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/db_cfront.pass.cpp
index e171883dc36..c9b2ba7c88e 100644
--- a/libcxx/test/std/strings/basic.string/string.access/db_cfront.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/db_cfront.pass.cpp
@@ -22,7 +22,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -42,8 +42,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/std/strings/basic.string/string.access/db_cindex.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/db_cindex.pass.cpp
index 770ab333c8b..c7b430efc98 100644
--- a/libcxx/test/std/strings/basic.string/string.access/db_cindex.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/db_cindex.pass.cpp
@@ -22,7 +22,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -44,8 +44,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/std/strings/basic.string/string.access/db_front.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/db_front.pass.cpp
index 7f2db649a12..73db2240510 100644
--- a/libcxx/test/std/strings/basic.string/string.access/db_front.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/db_front.pass.cpp
@@ -22,7 +22,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -46,8 +46,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/std/strings/basic.string/string.access/db_index.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/db_index.pass.cpp
index 40318e3988f..d3f2e8d28d0 100644
--- a/libcxx/test/std/strings/basic.string/string.access/db_index.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/db_index.pass.cpp
@@ -22,7 +22,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -44,8 +44,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/std/strings/basic.string/string.access/front.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/front.pass.cpp
index 5eee328feca..d51a12f0a77 100644
--- a/libcxx/test/std/strings/basic.string/string.access/front.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/front.pass.cpp
@@ -31,7 +31,7 @@ test(S s)
     assert(s.front() == typename S::value_type('z'));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -52,4 +52,6 @@ int main()
         assert(false);
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.access/index.pass.cpp b/libcxx/test/std/strings/basic.string/string.access/index.pass.cpp
index d529567c6fb..3a1224ca301 100644
--- a/libcxx/test/std/strings/basic.string/string.access/index.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.access/index.pass.cpp
@@ -20,7 +20,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -59,4 +59,6 @@ int main()
         assert(false);
     }
 #endif
+
+  return 0;
 }