From 06c5330a672970974fc77c9f7c1c8bfbb17cff5c Mon Sep 17 00:00:00 2001
From: Intel A80486DX2-66 <larry.holst@disroot.org>
Date: Sun, 10 Mar 2024 15:40:51 +0300
Subject: [PATCH] freadln.*: add testing against unexpected STDOUT flushing

---
 c-programming/io/freadln.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/c-programming/io/freadln.c b/c-programming/io/freadln.c
index 79e98cb..a4460ce 100644
--- a/c-programming/io/freadln.c
+++ b/c-programming/io/freadln.c
@@ -77,6 +77,24 @@ int freadln(FILE* f, char** output, size_t* length_out) {
 }
 
 #ifdef TEST
+# if defined(_WIN32) || defined(WIN32)
+#  include <windows.h>
+#  define SLEEP_FN Sleep
+#  define DO_SLEEP 1
+# elif defined(__CYGWIN__) || defined(__unix__) || defined(__APPLE__) && \
+	defined(__MACH__) || defined(__linux__) || defined(__FreeBSD__) || \
+	defined(__NetBSD__) || defined(__OpenBSD__) || defined(__bsdi__) || \
+	defined(__DragonFly__) || defined(__MINGW32__) || defined(__MINGW64__)
+#  include <unistd.h>
+#  define SLEEP_FN usleep
+#  define DO_SLEEP 1
+# else
+#  define DO_SLEEP 0
+# endif
+# if DO_SLEEP
+#  include <time.h>
+# endif
+
 int main(void) {
 	// stdin test
 	printf("Type something> ");
@@ -101,7 +119,16 @@ int main(void) {
 		exit(EXIT_FAILURE);
 	}
 	f = new_f;
+
+	printf("Waiting for 4 seconds...\n");
+	fflush(stdout);
+
+	clock_t start;
 	for (int i = 0; i < 4; i++) {
+#if DO_SLEEP
+		start = clock();
+#endif
+
 		size_t line_length;
 		int result = freadln(f, &line, &line_length);
 		if (result == freadln_ERROR) {
@@ -114,8 +141,12 @@ int main(void) {
 		}
 		printf("File, line #%d: '%s' (%zu characters)\n", i + 1, line,
 		       line_length);
+
+		SLEEP_FN(1000 - ((long double) (clock() - start) * 1000.l) /
+		         CLOCKS_PER_SEC);
 	}
 	fclose(f);
+	fflush(stdout);
 
 	return 0;
 }