unix: Don't use -Wno-error=cpp or #warning; fix strict alias warning.

For the sake of older versions of gcc (and other compilers), don't use
the #warning CPP directive, nor the -Wno-error=cpp option.

Also, fix a strict alias warning in modffi.c for older compilers, and
add a test for ffi module.

Addresses issue #847.

6 files changed, 29 insertions, 5 deletions

diff --git a/tests/run-tests b/tests/run-tests
index 8e7d2f2575..15eedc43c4 100755
--- a/tests/run-tests
+++ b/tests/run-tests
@@ -149,7 +149,7 @@ def main():
         if args.test_dirs is None:
             if pyb is None:
                 # run PC tests
-                test_dirs = ('basics', 'micropython', 'float', 'import', 'io', 'misc', 'unicode')
+                test_dirs = ('basics', 'micropython', 'float', 'import', 'io', 'misc', 'unicode', 'unix')
             else:
                 # run pyboard tests
                 test_dirs = ('basics', 'micropython', 'float', 'pyb', 'pybnative', 'inlineasm')
diff --git a/tests/unix/ffi_float.py b/tests/unix/ffi_float.py
new file mode 100644
index 0000000000..96a5ceeca6
--- /dev/null
+++ b/tests/unix/ffi_float.py
@@ -0,0 +1,21 @@
+# test ffi float support
+
+import ffi
+
+def ffi_open(names):
+    err = None
+    for n in names:
+        try:
+            mod = ffi.open(n)
+            return mod
+        except OSError as e:
+            err = e
+    raise err
+
+libc = ffi_open(('libc.so', 'libc.so.0', 'libc.so.6'))
+
+strtof = libc.func("f", "strtof", "sp")
+print('%.6f' % strtof('1.23', None))
+
+strtod = libc.func("d", "strtod", "sp")
+print('%.6f' % strtod('1.23', None))
diff --git a/tests/unix/ffi_float.py.exp b/tests/unix/ffi_float.py.exp
new file mode 100644
index 0000000000..e6fd5b7292
--- /dev/null
+++ b/tests/unix/ffi_float.py.exp
@@ -0,0 +1,2 @@
+1.230000
+1.230000
diff --git a/unix/Makefile b/unix/Makefile
index 9d035cab76..fff6fe0944 100644
--- a/unix/Makefile
+++ b/unix/Makefile
@@ -18,7 +18,7 @@ INC += -I$(PY_SRC)
 INC += -I$(BUILD)
 
 # compiler settings
-CWARN = -Wall -Werror -Wno-error=cpp
+CWARN = -Wall -Werror
 CFLAGS = $(INC) $(CWARN) -ansi -std=gnu99 -DUNIX $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
 
 # Debugging/Optimization
diff --git a/unix/modffi.c b/unix/modffi.c
index c788f5dd26..e019e9fc95 100644
--- a/unix/modffi.c
+++ b/unix/modffi.c
@@ -146,8 +146,8 @@ STATIC mp_obj_t return_ffi_value(ffi_arg val, char type)
         case 'v':
             return mp_const_none;
         case 'f': {
-            float *p = (float*)&val;
-            return mp_obj_new_float(*p);
+            union { ffi_arg ffi; float flt; } val_union = { .ffi = val };
+            return mp_obj_new_float(val_union.flt);
         }
         case 'd': {
             double *p = (double*)&val;
diff --git a/unix/modsocket.c b/unix/modsocket.c
index be97441af2..76787184a0 100644
--- a/unix/modsocket.c
+++ b/unix/modsocket.c
@@ -371,7 +371,8 @@ STATIC mp_obj_t mod_socket_getaddrinfo(mp_uint_t n_args, const mp_obj_t *args) {
         hints.ai_flags = AI_NUMERICSERV;
 #ifdef __UCLIBC_MAJOR__
 #if __UCLIBC_MAJOR__ == 0 && (__UCLIBC_MINOR__ < 9 || (__UCLIBC_MINOR__ == 9 && __UCLIBC_SUBLEVEL__ <= 32))
-#warning Working around uClibc bug with numeric service name
+// "warning" requires -Wno-cpp which is a relatively new gcc option, so we choose not to use it.
+//#warning Working around uClibc bug with numeric service name
         // Older versions og uClibc have bugs when numeric ports in service
         // arg require also hints.ai_socktype (or hints.ai_protocol) != 0
         // This actually was fixed in 0.9.32.1, but uClibc doesn't allow to