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.

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')

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))

tests/unix/ffi_float.py.exp

@@ -0,0 +1,2 @@
+1.230000
+1.230000

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

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;

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