Fix compilation on MinGW and other platforms without err.h

Port Steffen Jaeckel's fix from sjaeckel/heatshrink commit a98ba4612... to the latest Heatshrink source.

heatshrink.c

@@ -4,7 +4,6 @@
 #include <stdint.h>
 #include <assert.h>
 #include <string.h>
-#include <err.h>
 #include <fcntl.h>
 
 #include "heatshrink_encoder.h"
@@ -21,6 +20,18 @@
 #define LOG(...) /* NO-OP */
 #endif
 
+#if _WIN32
+#include <errno.h>
+#define HEATSHRINK_ERR(retval, ...) do { \
+fprintf(stderr, __VA_ARGS__); \
+fprintf(stderr, "Undefined error: %d\n", errno); \
+exit(retval); \
+} while(0)
+#else
+#include <err.h>
+#define HEATSHRINK_ERR(...) err(__VA_ARGS__)
+#endif
+
 static const int version_major = HEATSHRINK_VERSION_MAJOR;
 static const int version_minor = HEATSHRINK_VERSION_MINOR;
 static const int version_patch = HEATSHRINK_VERSION_PATCH;
@@ -122,7 +133,7 @@ static io_handle *handle_open(char *fname, IO_mode m, size_t buf_sz) {
 
     if (io->fd == -1) {         /* failed to open */
         free(io);
-        err(1, "open");
+        HEATSHRINK_ERR(1, "open");
         return NULL;
     }
 
@@ -154,10 +165,10 @@ static ssize_t handle_read(io_handle *io, size_t size, uint8_t **buf) {
         io->fill -= io->read;
         io->read = 0;
         ssize_t read_sz = read(io->fd, &io->buf[io->fill], io->size - io->fill);
-        if (read_sz < 0) { err(1, "read"); }
+        if (read_sz < 0) { HEATSHRINK_ERR(1, "read"); }
         io->total += read_sz;
         if (read_sz == 0) {     /* EOF */
-            if (close(io->fd) < 0) { err(1, "close"); }
+            if (close(io->fd) < 0) { HEATSHRINK_ERR(1, "close"); }
             io->fd = -1;
         }
         io->fill += read_sz;
@@ -192,7 +203,7 @@ static ssize_t handle_sink(io_handle *io, size_t size, uint8_t *input) {
         ssize_t written = write(io->fd, io->buf, io->fill);
         LOG("@ flushing %zd, wrote %zd\n", io->fill, written);
         io->total += written;
-        if (written == -1) { err(1, "write"); }
+        if (written == -1) { HEATSHRINK_ERR(1, "write"); }
         memmove(io->buf, &io->buf[written], io->fill - written);
         io->fill -= written;
     }
@@ -207,7 +218,7 @@ static void handle_close(io_handle *io) {
             ssize_t written = write(io->fd, io->buf, io->fill);
             io->total += written;
             LOG("@ close: flushing %zd, wrote %zd\n", io->fill, written);
-            if (written == -1) { err(1, "write"); }
+            if (written == -1) { HEATSHRINK_ERR(1, "write"); }
         }
         close(io->fd);
         io->fd = -1;
@@ -281,7 +292,7 @@ static int encode(config *cfg) {
         if (handle_drop(in, read_sz) < 0) { die("drop"); }
     };
 
-    if (read_sz == -1) { err(1, "read"); }
+    if (read_sz == -1) { HEATSHRINK_ERR(1, "read"); }
 
     heatshrink_encoder_free(hse);
     close_and_report(cfg);
@@ -358,7 +369,7 @@ static int decode(config *cfg) {
             if (handle_drop(in, read_sz) < 0) { die("drop"); }
         }
     }
-    if (read_sz == -1) { err(1, "read"); }
+    if (read_sz == -1) { HEATSHRINK_ERR(1, "read"); }
         
     heatshrink_decoder_free(hsd);
     close_and_report(cfg);