completely broken mingw code

Clueless I am, and not having a machine to test this one does not help.

.github/workflows/ci.yml

@@ -27,10 +27,14 @@ jobs:
     steps:
     - name: Check out
       uses: actions/checkout@v2
-    - name: Build and test
+    - name: Build
+      shell: bash
       run: |
         mkdir build
         cd build
         cmake .. -G "${{matrix.platform.generator}}"
         cmake --build .
+    - name: Test
+      shell: bash
+      run: |
         CTEST_OUTPUT_ON_FAILURE=1 ctest .

test/clar.c

@@ -6,7 +6,12 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/stat.h>
-#include <sys/wait.h>
+#if defined(__MINGW__) || defined(__MSYS__) || defined(__MINGW32__)
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+#else
+# include <sys/wait.h>
+#endif
 
 #include "clar.h"
 
@@ -59,6 +64,90 @@ static char *read_file(const char *path)
 
 static void run(const char *expected_output_file, int expected_error_code, ...)
 {
+#ifdef __MINGW32__
+	SECURITY_ATTRIBUTES sec_attributes = { 0 };
+	PROCESS_INFORMATION process_info = { 0 };
+	STARTUPINFO startup_info = { 0 };
+	char cmdline[4096] = { 0 };
+	char *expected_output = NULL;
+	char *output = NULL;
+	size_t output_size = 0;
+	HANDLE pipe_write;
+	HANDLE pipe_read;
+	DWORD exit_code;
+	va_list ap;
+
+	/*
+	 * Assemble command line arguments. In theory we'd have to properly
+	 * quote them. In practice none of our tests actually care.
+	 */
+	va_start(ap, expected_error_code);
+	snprintf(cmdline, sizeof(cmdline), "%s", SELFTEST_BINARY_PATH);
+	while (1) {
+		size_t cmdline_len = strlen(cmdline);
+		const char *arg;
+
+		arg = va_arg(ap, const char *);
+		if (!arg)
+			break;
+
+		cl_assert(cmdline_len + strlen(arg) < sizeof(cmdline));
+		snprintf(cmdline + cmdline_len, sizeof(cmdline) - cmdline_len,
+			 " %s", arg);
+	}
+	va_end(ap);
+
+	/*
+	 * Create a pipe that we will use to read data from the child process.
+	 * The writing side needs to be inheritable such that the child can use
+	 * it as stdout and stderr. The reading side should only be used by the
+	 * parent.
+	 */
+	sec_attributes.nLength = sizeof(sec_attributes);
+	sec_attributes.bInheritHandle = TRUE;
+	cl_assert_equal_b(1, CreatePipe(&pipe_read, &pipe_write, &sec_attributes, 0));
+	cl_assert_equal_b(1, SetHandleInformation(pipe_read, HANDLE_FLAG_INHERIT, 0));
+
+	/*
+	 * Create the child process with our pipe.
+	 */
+	startup_info.cb = sizeof(startup_info);
+	startup_info.hStdError = pipe_write;
+	startup_info.hStdOutput = pipe_write;
+	startup_info.dwFlags |= STARTF_USESTDHANDLES;
+	cl_assert_equal_b(1, CreateProcess("selftest", cmdline, NULL, NULL, TRUE, 0,
+					   NULL, NULL, &startup_info, &process_info));
+	cl_assert_equal_b(1, CloseHandle(&pipe_write));
+
+	while (1) {
+		CHAR buf[4096];
+		DWORD bytes_read;
+
+		cl_assert_equal_b(1, ReadFile(pipe_read, buf, sizeof(buf),
+					      &bytes_read, NULL));
+		if (!bytes_read)
+			break;
+
+		output = realloc(output, output_size + bytes_read);
+		cl_assert(output);
+		memcpy(output + output_size, buf, bytes_read);
+		output_size += bytes_read;
+	}
+
+	output = realloc(output, output_size + 1);
+	cl_assert(output);
+	output[output_size] = '\0';
+
+	cl_assert_equal_b(1, CloseHandle(&pipe_read));
+	cl_assert_equal_b(1, GetExitCodeProcess(process_info.hProcess, &exit_code));
+
+	expected_output = read_file(cl_fixture(expected_output_file));
+	cl_assert_equal_s(output, expected_output);
+	cl_assert_equal_i(exit_code, expected_error_code);
+
+	free(expected_output);
+	free(output);
+#else
 	const char *argv[16];
 	int pipe_fds[2];
 	va_list ap;
@@ -111,6 +200,7 @@ static void run(const char *expected_output_file, int expected_error_code, ...)
 	} else {
 		cl_fail("Fork failed.");
 	}
+#endif
 }
 
 void test_clar__help(void)