diff --git a/lib/std/libc/libc.c3 b/lib/std/libc/libc.c3
index e84796a93..0cf6af10b 100644
--- a/lib/std/libc/libc.c3
+++ b/lib/std/libc/libc.c3
@@ -20,6 +20,22 @@ struct LongDivResult
 	CLong rem;
 }
 
+struct Fpos_t @if(!env::WIN32)
+{
+	long __pos;
+	Mbstate_t __state;
+}
+
+struct Mbstate_t @if(!env::WIN32)
+{
+	int __count;
+	union __value
+	{
+		uint __wch;
+		char[4] __wcb;
+	}
+}
+
 fn Errno errno()
 {
 	return (Errno)os::errno();
@@ -35,7 +51,7 @@ def TerminateFunction = fn void();
 def CompareFunction = fn int(void*, void*);
 def JmpBuf = uptr[$$JMP_BUF_SIZE];
 def Fd = CInt;
-def Fpos_t = long; // TODO make sure fpos is correct on all targets.
+def Fpos_t = long @if(env::WIN32);
 def SignalFunction = fn void(CInt);
 
 const CInt SIGHUP = 1;
@@ -68,12 +84,12 @@ module libc @if(env::LIBC);
 extern fn void abort();
 extern fn CInt abs(CInt n);
 extern fn ZString asctime(Tm* timeptr);
-extern fn ZString asctime_r(Tm* timeptr, char* buf);
+extern fn ZString asctime_r(Tm* timeptr, char* buf) @if(!env::WIN32);
 extern fn CInt atexit(TerminateFunction func);
 extern fn double atof(char* str);
 extern fn int atoi(char* str);
 extern fn CLongLong atoll(char* str);
-extern fn void bsearch(void* key, void *base, usz items, usz size, CompareFunction compare);
+extern fn void* bsearch(void* key, void* base, usz items, usz size, CompareFunction compare);
 extern fn void* calloc(usz count, usz size);
 extern fn void clearerr(CFile stream);
 extern fn Clock_t clock();
@@ -107,7 +123,7 @@ extern fn CInt getchar();
 extern fn ZString getenv(ZString name);
 extern fn ZString gets(char* buffer);
 extern fn Tm* gmtime(Time_t* timer);
-extern fn Tm* gmtime_r(Time_t *timer, Tm* buf) @if(!env::WIN32);
+extern fn Tm* gmtime_r(Time_t* timer, Tm* buf) @if(!env::WIN32);
 extern fn CInt isatty(Fd fd) @if(!env::WIN32);
 extern fn CLong labs(CLong x);
 extern fn LongDivResult ldiv(CLong number, CLong denom);
@@ -169,7 +185,7 @@ extern fn CLong strtol(char* str, char** endptr, CInt base);
 extern fn CULong strtoul(char* str, char** endptr, CInt base);
 extern fn usz strxfrm(char* dest, ZString src, usz n);
 extern fn CInt system(ZString str);
-extern fn Time_t timegm(Tm *timeptr) @if(!env::WIN32);
+extern fn Time_t timegm(Tm* timeptr) @if(!env::WIN32);
 extern fn ZString tmpnam(ZString str);
 extern fn CFile tmpfile();
 extern fn CInt ungetc(CInt c, CFile stream);
@@ -180,8 +196,8 @@ extern fn CFile fmemopen(void* ptr, usz size, ZString mode);
 extern fn isz getline(char** linep, usz* linecapp, CFile stream);
 extern fn CInt timespec_get(TimeSpec* ts, CInt base);
 extern fn CInt nanosleep(TimeSpec* req, TimeSpec* remaining);
-extern fn ZString ctime(Time_t *timer);
-extern fn Time_t time(Time_t *timer);
+extern fn ZString ctime(Time_t* timer);
+extern fn Time_t time(Time_t* timer);
 
 const CInt STDIN_FD = 0;
 const CInt STDOUT_FD = 1;
@@ -405,7 +421,7 @@ struct Tm
 	CInt	tm_yday;	// days since January 1 [0-365]
 	CInt	tm_isdst;	// Daylight Savings Time flag
 	TimeOffset tm_gmtoff @if(!env::WIN32);	/* offset from UTC in seconds */
-	char *tm_zone @if(!env::WIN32);	/* timezone abbreviation */
+	char* tm_zone @if(!env::WIN32);	/* timezone abbreviation */
 	CInt tm_nsec @if(env::WASI);
 }
 
@@ -418,7 +434,7 @@ struct TimeSpec
 
 
 def Clock_t = int @if(env::WIN32);
-def Clock_t = CULong @if(!env::WIN32);
+def Clock_t = CLong @if(!env::WIN32);
 
 def TimeOffset = int @if(env::WASI) ;
 def TimeOffset = CLong @if(!env::WASI) ;
@@ -426,8 +442,10 @@ def TimeOffset = CLong @if(!env::WASI) ;
 const int TIME_UTC = 1;
 
 
-// Likely wrong, must be per platform.
-const CLOCKS_PER_SEC = 1000000;
+// This is a best-effort aproximation, but the C standard does not enforce
+// that this is a compile-time standard.
+const CLOCKS_PER_SEC @if(env::WIN32) = 1000;
+const CLOCKS_PER_SEC @if(!env::WIN32) = 1000000;
 
 module libc::errno;
 
diff --git a/test/unit/stdlib/libc/libc.c3 b/test/unit/stdlib/libc/libc.c3
new file mode 100644
index 000000000..8525909c6
--- /dev/null
+++ b/test/unit/stdlib/libc/libc.c3
@@ -0,0 +1,577 @@
+module libc_tests;
+import libc;
+
+// Functions from libc.c3 which do not have a test are still present in
+// comments here in the same order that they occur within libc.c3
+
+fn void abort() @test
+{
+	// Cannot actually test this, so just checking if it's defined.
+	assert($defined(libc::abort));
+}
+
+fn void abs() @test
+{
+	CInt x = 21;
+	assert(libc::abs(x) == 21);
+	assert(libc::abs(-x) == 21);
+	$assert @typeis(libc::abs(x), CInt);
+	$assert @typeis(libc::abs(-x), CInt);
+}
+
+fn void asctime() @test
+{
+	Tm time = {
+		.tm_sec = 13,
+		.tm_min = 42,
+		.tm_hour = 3,
+		.tm_mday = 5,
+		.tm_mon = 8,
+		.tm_year = 11,
+		.tm_wday = 1,
+		.tm_yday = 41,
+		.tm_isdst = 0
+	};
+	ZString formatted_time = libc::asctime(&time);
+	assert(libc::strcmp(formatted_time, "Mon Sep  5 03:42:13 1911\n") == 0);
+}
+
+fn void asctime_r() @test @if(!env::WIN32)
+{
+	Tm time = {
+		.tm_sec = 13,
+		.tm_min = 42,
+		.tm_hour = 3,
+		.tm_mday = 5,
+		.tm_mon = 8,
+		.tm_year = 11,
+		.tm_wday = 1,
+		.tm_yday = 41,
+		.tm_isdst = 0
+	};
+	char[26] formatted_time;
+	libc::asctime_r(&time, &formatted_time);
+	assert(libc::strcmp((ZString) &formatted_time, "Mon Sep  5 03:42:13 1911\n") == 0);
+}
+
+fn void test_atexit_function()
+{
+	assert(5 == 5);
+	// This correctly asserts, but does not fail the tests.
+	// char c = 2;
+	// assert(c == 5);
+}
+
+fn void atexit() @test
+{
+	// No idea how to test this, but we can at least check if this compiles
+	libc::atexit(&test_atexit_function);
+	libc::atexit(fn void() => 4);
+}
+
+fn void atof() @test
+{
+	assert(libc::atof("123.45") == 123.45);
+	$assert @typeis(libc::atof("123.45"), double);
+	assert(libc::atof("-3.14") == -3.14);
+	$assert @typeis(libc::atof("-3.14"), double);
+	assert(libc::atof("x") == 0.0);
+	$assert @typeis(libc::atof("x"), double);
+	assert(libc::atof("") == 0.0);
+	$assert @typeis(libc::atof(""), double);
+}
+
+fn void atoi() @test
+{
+	assert(libc::atoi("123") == 123);
+	$assert @typeis(libc::atoi("123"), int);
+	assert(libc::atoi("-3.14") == -3);
+	$assert @typeis(libc::atoi("-3.14"), int);
+	assert(libc::atoi("x") == 0);
+	$assert @typeis(libc::atoi("x"), int);
+	assert(libc::atoi("") == 0);
+	$assert @typeis(libc::atoi(""), int);
+}
+
+fn void atoll() @test
+{
+	assert(libc::atoi("123") == 123);
+	$assert @typeis(libc::atoi("123"), int);
+	assert(libc::atoi("-3.14") == -3);
+	$assert @typeis(libc::atoi("-3.14"), int);
+	assert(libc::atoi("x") == 0);
+	$assert @typeis(libc::atoi("x"), int);
+	assert(libc::atoi("") == 0);
+	$assert @typeis(libc::atoi(""), int);
+}
+
+// Compare function, struct and function for libc::bsearch test
+fn int compare_cint(void* a, void* b)
+{
+	CInt a_i = *((CInt*) a);
+	CInt b_i = *((CInt*) b);
+	return a_i - b_i;
+}
+
+struct Event
+{
+	CInt day;
+	CInt month;
+	String desc;
+}
+
+fn int compare_event(void* a, void* b)
+{
+  Event* a_e = a; // Avoid casts if possible
+  Event* b_e = b;
+  return (a_e.month - b_e.month) * 100 + a_e.day - b_e.day;
+}
+
+fn void bsearch() @test
+{
+	CInt[] int_ar = { 0, 1, 2, 3, 4, 5, 6 };
+	CInt key = 0;
+	CInt* found = (CInt*) libc::bsearch(&key, int_ar, 7, CInt.sizeof, &compare_cint);
+	assert(*found == 0);
+	key = 1;
+	found = (CInt*) libc::bsearch(&key, int_ar, 7, CInt.sizeof, &compare_cint);
+	assert(*found == 1);
+	key = 2;
+	found = (CInt*) libc::bsearch(&key, int_ar, 7, CInt.sizeof, &compare_cint);
+	assert(*found == 2);
+	key = 5;
+	found = (CInt*) libc::bsearch(&key, int_ar, 7, CInt.sizeof, &compare_cint);
+	assert(*found == 5);
+	key = 6;
+	found = (CInt*) libc::bsearch(&key, int_ar, 7, CInt.sizeof, &compare_cint);
+	assert(*found == 6);
+	CInt non_existant_key = 12;
+	found = (CInt*) libc::bsearch(&non_existant_key, int_ar, 7, CInt.sizeof, &compare_cint);
+	assert(found == null);
+
+	Event[] events = {
+		{ 2, 1, "2nd of February" },
+		{ 5, 1, "Some day" },
+		{ 1, 5, "Begin of May" },
+		{ 1, 7, "Summer holiday start" },
+		{ 21, 7, "A fine warm day" },
+		{ 11, 11, "Peace" },
+		{ 25, 12, "Family and sharing" },
+		{ 31, 12, "End of the year" }
+	};
+	Event searching = { .day = 1, .month = 5 };
+	Event* found1 = (Event*) libc::bsearch(&searching, events, 7, Event.sizeof, &compare_event);
+	assert(found1.desc == "Begin of May");
+	searching = { .day = 4, .month = 4 };
+	found1 = (Event*) libc::bsearch(&searching, events, 7, Event.sizeof, &compare_event);
+	assert(found1 == null);
+}
+
+fn void calloc() @test
+{
+	usz amount = 10;
+	CInt* int_ar = libc::calloc(amount, CInt.sizeof);
+	for (usz i = 0; i < amount; i++)
+	{
+		assert(int_ar[i] == 0);
+	}
+	libc::free(int_ar);
+}
+
+fn void clearerr_feof_ferror() @test
+{
+	CFile* tmpf = libc::tmpfile();
+	// Example from cppreference.com
+	ZString test_string = (ZString) "cppreference.com\n" +++ '\0';
+	libc::fputs(test_string, tmpf);
+	libc::rewind(tmpf);
+
+	for (int i = 0; i < test_string.len(); i++)
+	{
+		int c = libc::fgetc(tmpf);
+		assert(c != libc::EOF);
+		assert(c == test_string[i]);
+	}
+
+	assert(libc::fgetc(tmpf) == libc::EOF);
+	assert(libc::feof(tmpf) != 0);
+	// there should be no errors (EOF is not an error)
+	assert(libc::ferror(tmpf) == 0);
+	libc::clearerr(tmpf);
+	assert(libc::feof(tmpf) == 0);
+}
+
+fn void clock() @test
+{
+	Clock_t time1 = libc::clock();
+	if (time1 < 0)
+	{
+		// If getting processor-time is not available, do nothing
+		return;
+	}
+	// Waist bit of time
+	int i = 0;
+	for (int j = 0; j <= 1000; j++)
+	{
+		i += j;
+	}
+	assert(i == (1000 / 2) * (1000 + 1)); // Gauss, prevent compiler-optimisation
+	Clock_t time2 = libc::clock();
+	assert(time2 >= time1);
+}
+
+fn void close() @test @if(!env::WIN32)
+{
+	assert(libc::close(13) == -1);
+	// NOTE: errno is part of libc, and is thus recursively imported
+	assert(libc::errno() == errno::EBADF);
+}
+
+fn void difftime() @test
+{
+	Time_t t1 = 1293;
+	Time_t t2 = 919919;
+	assert(libc::difftime(t2, t1) > 0);
+	assert(libc::difftime(t1, t2) < 0);
+}
+
+fn void div() @test
+{
+	DivResult res = libc::div(13, 2);
+	assert(res.quot == 6);
+	assert(res.rem == 1);
+	res = libc::div(-5, 3);
+	assert(res.quot == -1);
+	assert(res.rem == -2);
+}
+
+fn void exit() @test
+{
+	// Cannot actually test this, so just checking if it's defined.
+	assert($defined(libc::exit));
+}
+
+fn void fclose() @test
+{
+	CFile random_file = libc::tmpfile();
+	assert(libc::fclose(random_file) == 0);
+}
+
+fn void fdopen() @test @if(!env::WIN32)
+{
+	CFile stdin = libc::fdopen(-1, "w");
+	assert(libc::errno() == errno::EBADF);
+}
+
+fn void fflush() @test
+{
+	CFile stdin = libc::stdin();
+	assert(libc::fflush(stdin) == 0);
+}
+
+fn void fgets_fget() @test
+{
+	CFile* tmpf = libc::tmpfile();
+	// Example from cppreference.com
+	ZString test_string = (ZString) "cppreference.com\n" +++ '\0';
+	libc::rewind(tmpf);
+	libc::fclose(tmpf);
+}
+
+import std::io;
+fn void fseek_ftell_fgetpos_fsetpos_rewind() @test
+{
+	CFile* tmpf = libc::tmpfile();
+	// Example from cppreference.com
+	ZString test_string = (ZString) "cppreference.com\n" +++ '\0';
+	libc::fputs(test_string, tmpf);
+	libc::rewind(tmpf);
+
+	Fpos_t pos;
+	libc::fgetpos(tmpf, &pos);
+	assert(libc::fgetc(tmpf) == 'c');
+	assert(libc::fgetc(tmpf) == 'p');
+
+	libc::fsetpos(tmpf, &pos);
+	assert(libc::fgetc(tmpf) == 'c');
+	assert(libc::fgetc(tmpf) == 'p');
+
+	assert(libc::ftell(tmpf) == 2);
+
+	libc::fseek(tmpf, -2, libc::SEEK_END);
+	assert(libc::fgetc(tmpf) == 'm');
+	assert(libc::fgetc(tmpf) == '\n');
+
+	libc::fclose(tmpf);
+}
+
+// fn void fileno() @test {}
+// fn void fopen() @test {}
+// fn void fprintf() @test {}
+// fn void fputc() @test {}
+// fn void fputs() @test {}
+// fn void fread() @test {}
+// fn void freopen() @test {}
+// fn void fscanf() @test {}
+// fn void fseek() @test {}
+// fn void ftell() @test {}
+// fn void fwrite() @test {}
+// fn void getc() @test {}
+// fn void getchar() @test {}
+// fn void getenv() @test {}
+// fn void gets() @test {}
+// fn void gmtime() @test {}
+// fn void gmtime_r() @test {}
+// fn void isatty() @test {}
+// fn void labs() @test {}
+// fn void ldiv() @test {}
+// fn void localtime() @test {}
+// fn void localtime_r() @test {}
+// fn void longjmp() @test {}
+
+fn void malloc_free() @test
+{
+	CInt* ar = libc::malloc(3 * CInt.sizeof);
+	ar[0] = 10;
+	ar[1] = -10;
+	ar[2] = 4;
+	assert(ar[0] == 10);
+	assert(ar[1] == -10);
+	assert(ar[2] == 4);
+	libc::free(ar);
+}
+
+// fn void memchr() @test {}
+// fn void memcmp() @test {}
+// fn void memcpy() @test {}
+// fn void memmove() @test {}
+// fn void memset() @test {}
+// fn void mktime() @test {}
+// fn void perror() @test {}
+// fn void printf() @test {}
+// fn void putc() @test {}
+// fn void putchar() @test {}
+// fn void puts() @test {}
+// fn void qsort() @test {}
+// fn void raise() @test {}
+// fn void rand() @test {}
+// fn void read() @test {}
+// fn void realloc() @test {}
+// fn void remove() @test {}
+// fn void rename() @test {}
+// fn void scanf() @test {}
+// fn void setbuf() @test {}
+// fn void setenv() @test {}
+// fn void setjmp() @test {}
+// fn void setvbuf() @test {}
+// fn void signal() @test {}
+// fn void snprintf() @test {}
+// fn void sprintf() @test {}
+// fn void srand() @test {}
+// fn void sscanf() @test {}
+// fn void strcat() @test {}
+// fn void strchr() @test {}
+// fn void strcmp() @test {}
+// fn void strcoll() @test {}
+// fn void strcspn() @test {}
+// fn void strcpy() @test {}
+// fn void strerror() @test {}
+// fn void strftime() @test {}
+// fn void strlen() @test {}
+// fn void strncat() @test {}
+// fn void strncmp() @test {}
+// fn void strncpy() @test {}
+// fn void stroul() @test {}
+// fn void strpbrk() @test {}
+// fn void strspn() @test {}
+// fn void strptime() @test {}
+// fn void strrchr() @test {}
+// fn void strstr() @test {}
+// fn void strtod() @test {}
+// fn void strtof() @test {}
+// fn void strtok() @test {}
+// fn void strtol() @test {}
+// fn void strtoul() @test {}
+// fn void strxfrm() @test {}
+// fn void system() @test {}
+// fn void timegm() @test {}
+// fn void tmpnam() @test {}
+// fn void tmpfile() @test {}
+// fn void ungetc() @test {}
+// fn void unsetenv() @test {}
+// fn void write() @test {}
+//
+// extern fn CFile fmemopen(void* ptr, usz size, ZString mode);
+// extern fn isz getline(char** linep, usz* linecapp, CFile stream);
+// extern fn CInt timespec_get(TimeSpec* ts, CInt base);
+// extern fn CInt nanosleep(TimeSpec* req, TimeSpec* remaining);
+// extern fn ZString ctime(Time_t *timer);
+// extern fn Time_t time(Time_t *timer);
+//
+// const CInt STDIN_FD = 0;
+// const CInt STDOUT_FD = 1;
+// const CInt STDERR_FD = 2;
+//
+// module libc @if(env::LINUX);
+// extern CFile __stdin @extern("stdin");
+// extern CFile __stdout @extern("stdout");
+// extern CFile __stderr @extern("stderr");
+// extern fn usz malloc_usable_size(void* ptr);
+// macro usz malloc_size(void* ptr) => malloc_usable_size(ptr);
+// extern fn void* aligned_alloc(usz align, usz size);
+// macro CFile stdin() => __stdin;
+// macro CFile stdout() => __stdout;
+// macro CFile stderr() => __stderr;
+//
+// module libc @if(env::NETBSD || env::OPENBSD);
+// extern fn int fcntl(CInt socket, int cmd, ...);
+// extern fn int _setjmp(void*);
+// macro int setjmp(void* ptr) => _setjmp(ptr);
+// extern fn int _longjmp(void*, int);
+// macro usz longjmp(void* ptr, CInt i) => _longjmp(ptr, i);
+// extern fn usz malloc_size(void* ptr);
+// extern fn void* aligned_alloc(usz align, usz size);
+// macro CFile stdin() { return fdopen(0, "r"); }
+// macro CFile stdout() { return fdopen(1, "w"); }
+// macro CFile stderr() { return fdopen(2, "w"); }
+//
+// module libc @if(env::DARWIN || env::FREEBSD);
+// extern CFile __stdinp;
+// extern CFile __stdoutp;
+// extern CFile __stderrp;
+// extern fn usz malloc_size(void* ptr) @if(!env::FREEBSD);
+// extern fn void* aligned_alloc(usz align, usz size);
+// macro CFile stdin() => __stdinp;
+// macro CFile stdout() => __stdoutp;
+// macro CFile stderr() => __stderrp;
+//
+// module libc @if(env::FREEBSD);
+// extern fn usz malloc_usable_size(void* ptr);
+// macro usz malloc_size(void* ptr) => malloc_usable_size(ptr);
+//
+// module libc @if(env::WIN32);
+// macro usz malloc_size(void* ptr) => _msize(ptr);
+// macro CFile stdin() => __acrt_iob_func(STDIN_FD);
+// macro CFile stdout() => __acrt_iob_func(STDOUT_FD);
+// macro CFile stderr() => __acrt_iob_func(STDERR_FD);
+//
+// module libc @if(env::LIBC && !env::WIN32 && !env::LINUX && !env::DARWIN && !env::BSD_FAMILY);
+// macro CFile stdin() { return (CFile*)(uptr)STDIN_FD; }
+// macro CFile stdout() { return (CFile*)(uptr)STDOUT_FD; }
+// macro CFile stderr() { return (CFile*)(uptr)STDERR_FD; }
+//
+// module libc @if(!env::LIBC);
+//
+// fn void longjmp(JmpBuf* buffer, CInt value) @weak @extern("longjmp") @nostrip
+// {
+// 	unreachable("longjmp unavailable");
+// }
+//
+// fn CInt setjmp(JmpBuf* buffer) @weak @extern("setjmp") @nostrip
+// {
+// 	unreachable("setjmp unavailable");
+// }
+//
+// fn void* malloc(usz size) @weak @extern("malloc") @nostrip
+// {
+// 	unreachable("malloc unavailable");
+// }
+// fn void* calloc(usz count, usz size) @weak @extern("calloc") @nostrip
+// {
+// 	unreachable("calloc unavailable");
+// }
+// fn void* free(void*) @weak @extern("free")
+// {
+// 	unreachable("free unavailable");
+// }
+//
+// fn void* realloc(void* ptr, usz size) @weak @extern("realloc") @nostrip
+// {
+// 	unreachable("realloc unavailable");
+// }
+//
+// fn void* memcpy(void* dest, void* src, usz n) @weak @extern("memcpy") @nostrip
+// {
+// 	for (usz i = 0; i < n; i++) ((char*)dest)[i] = ((char*)src)[i];
+// 	return dest;
+// }
+//
+// fn void* memmove(void* dest, void* src, usz n) @weak @extern("memmove") @nostrip
+// {
+// 	return memcpy(dest, src, n) @inline;
+// }
+//
+// fn void* memset(void* dest, CInt value, usz n) @weak @extern("memset") @nostrip
+// {
+// 	for (usz i = 0; i < n; i++) ((char*)dest)[i] = (char)value;
+// 	return dest;
+// }
+//
+// fn int fseek(CFile stream, SeekIndex offset, int whence) @weak @extern("fseek") @nostrip
+// {
+// 	unreachable("'fseek' not available.");
+// }
+// fn CFile fopen(ZString filename, ZString mode) @weak @extern("fopen") @nostrip
+// {
+// 	unreachable("'fopen' not available.");
+// }
+//
+// fn CFile freopen(ZString filename, ZString mode, CFile stream) @weak @extern("fopen") @nostrip
+// {
+// 	unreachable("'freopen' not available.");
+// }
+//
+// fn usz fwrite(void* ptr, usz size, usz nmemb, CFile stream) @weak @extern("fwrite") @nostrip
+// {
+// 	unreachable("'fwrite' not available.");
+// }
+//
+// fn usz fread(void* ptr, usz size, usz nmemb, CFile stream) @weak @extern("fread") @nostrip
+// {
+// 	unreachable("'fread' not available.");
+// }
+//
+// fn CFile fclose(CFile) @weak @extern("fclose") @nostrip
+// {
+// 	unreachable("'fclose' not available.");
+// }
+//
+// fn int fflush(CFile stream) @weak @extern("fflush") @nostrip
+// {
+// 	unreachable("'fflush' not available.");
+// }
+//
+// fn int fputc(int c, CFile stream) @weak @extern("fputc") @nostrip
+// {
+// 	unreachable("'fputc' not available.");
+// }
+//
+// fn char* fgets(ZString str, int n, CFile stream) @weak @extern("fgets") @nostrip
+// {
+// 	unreachable("'fgets' not available.");
+// }
+//
+// fn int fgetc(CFile stream) @weak @extern("fgetc") @nostrip
+// {
+// 	unreachable("'fgetc' not available.");
+// }
+//
+// fn int feof(CFile stream) @weak @extern("feof") @nostrip
+// {
+// 	unreachable("'feof' not available.");
+// }
+//
+// fn int putc(int c, CFile stream) @weak @extern("putc") @nostrip
+// {
+// 	unreachable("'putc' not available.");
+// }
+// fn int putchar(int c) @weak @extern("putchar") @nostrip
+// {
+// 	unreachable("'putchar' not available.");
+// }
+// fn int puts(ZString str) @weak @extern("puts") @nostrip
+// {
+// 	unreachable("'puts' not available.");
+// }
+//
+// module libc;
diff --git a/test/unit/stdlib/libc/libc_extra.c3 b/test/unit/stdlib/libc/libc_extra.c3
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/unit/stdlib/libc/os/darwin.c3 b/test/unit/stdlib/libc/os/darwin.c3
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/unit/stdlib/libc/os/errno.c3 b/test/unit/stdlib/libc/os/errno.c3
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/unit/stdlib/libc/os/freebsd.c3 b/test/unit/stdlib/libc/os/freebsd.c3
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/unit/stdlib/libc/os/linux.c3 b/test/unit/stdlib/libc/os/linux.c3
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/unit/stdlib/libc/os/posix.c3 b/test/unit/stdlib/libc/os/posix.c3
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/unit/stdlib/libc/os/win32.c3 b/test/unit/stdlib/libc/os/win32.c3
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/unit/stdlib/libc/termios.c3 b/test/unit/stdlib/libc/termios.c3
new file mode 100644
index 000000000..e69de29bb