Add an example of M_LET_IF

example/ex-defer01.c

@@ -0,0 +1,36 @@
+#include "m-core.h"
+
+// Stubs defined for the example. Real code will use soundio library.
+struct SoundIo { int x; };
+struct SoundIoDevice { int x; };
+struct SoundIoOutStream { int x; };
+
+static struct SoundIo *soundio_create(void) { return (struct SoundIo *) malloc(sizeof(struct SoundIo)); }
+static void soundio_destroy(struct SoundIo *s) { free(s); }
+
+static struct SoundIoDevice *soundio_get_device(struct SoundIo *io, int def) { (void) io; (void) def; return (struct SoundIoDevice *) malloc(sizeof(struct SoundIoDevice)); }
+static void soundio_device_unref(struct SoundIoDevice *s) { free(s); }
+
+static struct SoundIoOutStream *soundio_outstream_create(struct SoundIoDevice *device) { (void) device ; return (struct SoundIoOutStream *) malloc(sizeof(struct SoundIoOutStream)); }
+static void soundio_outstream_destroy(struct SoundIoOutStream *s) { free(s); }
+
+static bool soundio_wait_events(struct SoundIo *s) { (void) s; return false; }
+// End of stubs
+
+int main(void)
+{
+  int err = 1;
+
+  /* Example of using M_LET_IF macro to simplify writing error handling code.
+     The following code creates some object, test if the object creation succeeds, register the destructor, and print an error if something went wrong
+  */
+  M_LET_IF( struct SoundIo *soundio = soundio_create(), soundio != 0 , soundio_destroy(soundio) , fprintf(stderr, "out of memory for soundio\n") )
+    M_LET_IF(struct SoundIoDevice *device = soundio_get_device(soundio, -1), device != 0, soundio_device_unref(device),  fprintf(stderr, "out of memory for device\n"))
+    M_LET_IF(struct SoundIoOutStream *outstream = soundio_outstream_create(device), outstream != 0, soundio_outstream_destroy(outstream), fprintf(stderr, "out of memory for stream\n")) {
+    err = 0;
+    bool cont = true;
+    while (cont)
+      cont = soundio_wait_events(soundio);
+  }
+  return err;
+}