Support dprintf on systems where it isn't natively available

This fixes issue #35 by implementing dprintf using sprintf and write.
#35

This is based on work by greengoblinbear in pull request #36:
#36

Author: ben-brewer-codethink

Makefile

@@ -3,7 +3,7 @@ FRONTEND_DEBUG = $(FRONTEND)-debug
 
 BASE = src/
 
-SRC_DIR = . prep parse sema global parse/stmt sema/stmt sema/pass
+SRC_DIR = . util prep parse sema global parse/stmt sema/stmt sema/pass
 SRC_DIR_BASE = $(addprefix $(BASE),$(SRC_DIR))
 
 GCC_VER_MAJ = $(shell $(CC) -dumpversion | cut -f 1 -d '.')

include/ofc/util/dprintf.h

@@ -0,0 +1,30 @@
+/* Copyright 2017 Codethink Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __ofc_dprintf_h__
+#define __ofc_dprintf_h__
+
+#include <stdio.h>
+
+#if defined(_GNU_SOURCE) || (_XOPEN_SOURCE >= 700) || (_POSIX_C_SOURCE >= 200809L)
+#define NATIVE_DPRINTF
+#endif
+
+#ifndef NATIVE_DPRINTF
+int dprintf(int fd, const char *format, ...)
+	__attribute__ ((format (printf, 2, 3)));
+#endif
+
+#endif

src/colstr.c

@@ -19,6 +19,7 @@
 #include <ctype.h>
 
 #include "ofc/colstr.h"
+#include "ofc/util/dprintf.h"
 
 
 struct ofc_colstr_s

src/util/dprintf.c

@@ -0,0 +1,46 @@
+/* Copyright 2017 Codethink Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ofc/util/dprintf.h"
+#include <stdarg.h>
+#include <unistd.h>
+
+#ifndef NATIVE_DPRINTF
+int dprintf(int fd, const char *format, ...)
+{
+	va_list args;
+	va_start(args, format);
+
+	va_list largs;
+	va_copy(largs, args);
+	int len = vsnprintf(NULL, 0, format, largs);
+	va_end(largs);
+
+	if (len <= 0)
+	{
+		va_end(args);
+		return len;
+	}
+
+	char buff[len + 1];
+	int plen = vsnprintf(buff, (len + 1), format, args);
+	va_end(args);
+
+	if (len != plen)
+		return -1;
+
+	return (int)write(fd, buff, len);
+}
+#endif