Test assumptions about variadic re-packing

This test uses the same style of re-packing variadic arguments through
two layers of variadic calls, and compares that call chain against one
direct variadic call.

The outer function uses the same kind of re-packing used in
src/libfaketime.c's syscall (leading to real_syscall), but the inner
functions use different assumptions about the types of each argument.

This is not an entirely comprehensive test, because we only define two
different inner function signatures.  If some particular syscall is
breaking when intercepted, consider adding something like its expected
function signature in test/variadic/inner.c, and invoke it in
test/variadic/main.c.

Note that we don't test any floating point types (those types are
typically passed in registers in x86-64, not on the stack, and are
also not used for any syscall that i'm aware of).

test/Makefile

@@ -33,6 +33,13 @@ functest:
 randomtest: repeat_random
 	./randomtest.sh
 
+# ensure our variadic argument unpacking/repacking works as expected
+confirm_variadic_promotion: variadic_promotion
+	./variadic_promotion
+variadic_promotion: variadic/main.o variadic/outer.o variadic/inner.o
+	${CC} -o $@ ${CFLAGS} $^
+variadic/%.o: variadic/%.c
+	${CC} -c -o $@ ${CFLAGS} $<
 
 # run snippet tests
 snippets: test_variable_data test_library_constructors
@@ -59,7 +66,7 @@ use_lib_%: _use_lib_test.c snippets/%.c lib%.so
 ## cleanup and metainformation
 
 clean:
-	@rm -f ${OBJ} timetest getrandom_test syscall_test $(foreach f,${TEST_SNIPPETS},use_lib_${f} lib${f}.so run_${f})
+	@rm -f ${OBJ} timetest getrandom_test syscall_test $(foreach f,${TEST_SNIPPETS},use_lib_${f} lib${f}.so run_${f}) variadic_promotion variadic/*.o
 
 distclean: clean
 	@echo

test/variadic/inner.c

@@ -0,0 +1,46 @@
+
+#include <stdio.h>
+#include <wchar.h>
+#include <stdarg.h>
+#include <stddef.h>
+
+/*   round 0:  c, s, wc, i, wi */
+long inner0(char *out, ...) {
+  char c = 0;
+  short s = 0;
+  wchar_t wc = 0;
+  int i = 0;
+  wint_t wi = 0;
+
+  va_list ap;
+  va_start(ap, out);
+  c = va_arg(ap, int);
+  s = va_arg(ap, int);
+  wc = va_arg(ap, typeof(wc));
+  i = va_arg(ap, typeof(i));
+  wi = va_arg(ap, typeof(wi));
+  va_end(ap);
+
+  int ret = sprintf(out, "c: 0x%x s: 0x%x wc: 0x%lx i: 0x%x wi: 0x%x\n", c, s, (long)wc, i, wi);
+  return ret;
+}
+/*   round 1: l, ll, ptr, pd, sz */
+long inner1(char *out, ...) {
+  long l = 0;
+  long long ll = 0;
+  void *ptr = NULL;
+  ptrdiff_t pd = 0;
+  size_t sz = 0;
+
+  va_list ap;
+  va_start(ap, out);
+  l = va_arg(ap, typeof(l));
+  ll = va_arg(ap, typeof(ll));
+  ptr = va_arg(ap, typeof(ptr));
+  pd = va_arg(ap, typeof(pd));
+  sz = va_arg(ap, typeof(sz));
+  va_end(ap);
+
+  int ret = sprintf(out, "l: 0x%lx ll: 0x%llx ptr: %p pd: 0x%tx sz: 0x%zx\n", l, ll, ptr, pd, sz);
+  return ret;
+}

test/variadic/main.c

@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stddef.h>
+#include <wchar.h>
+
+extern long outer(long num, char *out, ...);
+extern long inner0(char *out, ...);
+extern long inner1(char *out, ...);
+
+#define bufsize 2048
+
+static int compare_buffers(int round,
+                            long ret_outer, long ret_inner,
+                            const char* outer, const char* inner) {
+  int ret = 0;
+  if (ret_outer != ret_inner) {
+    printf("Round %d: return values differ (outer: %ld inner: %ld)\n", round, ret_outer, ret_inner);
+    ret++;
+  }
+  if (memcmp(outer, inner, bufsize)) {
+    printf("Round %d strings differ:\n - outer: %s\n - inner: %s\n", round, outer, inner);
+    ret++;
+  }
+  if (ret == 0)
+    printf("Round %d success: %s\n", round, outer);
+  return ret;
+}
+
+int main() {
+/* sizes of intrinsic types as reported by echo | cpp -dM | grep
+   SIZEOF, pruned to avoid floating point types.  Should work with
+   both clang and gcc, not sure about other C preprocessors.
+
+   Note that we set bits in every high octet and every low octet to
+   see that they end up in the right spot.
+ */
+  char c =             0x03L;
+  short s =           (0x04L << ((__SIZEOF_SHORT__ - 1) * 8))     + 0xff;
+  wchar_t wc =        (0x05L << ((__SIZEOF_WCHAR_T__ - 1) * 8))   + 0xfe;
+  int i =             (0x06L << ((__SIZEOF_INT__  - 1) * 8))      + 0xfd;
+  wint_t wi =         (0x07L << ((__SIZEOF_WINT_T__ - 1) * 8))    + 0xfc;
+  long l =            (0x08L << ((__SIZEOF_LONG__ - 1) * 8) )     + 0xfb;
+  long long ll =      (0x09LL << ((__SIZEOF_LONG_LONG__ - 1) * 8)) + 0xfa;
+  void *ptr = (void*)((0x0aL << ((__SIZEOF_POINTER__ - 1) * 8))   + 0xf9);
+  ptrdiff_t pd =      (0x0bL << ((__SIZEOF_PTRDIFF_T__ -1) * 8))  + 0xf9;
+  size_t sz =         (0x0cL << ((__SIZEOF_SIZE_T__ - 1) * 8))    + 0xf8;
+
+  char *buf[2];
+  for (int j = 0; j < 2; j++)
+    buf[j] = malloc(bufsize);
+
+  int ret[2];
+  int errors = 0;
+
+#define reset_buffers(n) for (int j = 0; j < 2; j++) memset(buf[j], n, bufsize)
+#define check_buffers(n) errors += compare_buffers(n, ret[0], ret[1], buf[0], buf[1])
+
+  reset_buffers(0);
+  ret[0] = outer(0, buf[0], c, s, wc, i, wi);
+  ret[1] = inner0(buf[1], c, s, wc, i, wi);
+  check_buffers(0);
+
+  reset_buffers(1);
+  ret[0] = outer(1, buf[0], l, ll, ptr, pd, sz);
+  ret[1] = inner1(buf[1], l, ll, ptr, pd, sz);
+  check_buffers(1);
+
+  return (int)errors;
+}

test/variadic/outer.c

@@ -0,0 +1,21 @@
+#include <stdarg.h>
+#include <time.h>
+#include "../../src/faketime_common.h"
+
+extern long inner0(char *out, ...);
+extern long inner1(char *out, ...);
+
+long outer(long num, char *out, ...) {
+  va_list ap;
+  va_start(ap, out);
+  variadic_promotion_t a[syscall_max_args];
+  for (int i = 0; i < syscall_max_args; i++)
+    a[i] = va_arg(ap, variadic_promotion_t);
+  va_end(ap);
+
+  if (num == 0)
+    return inner0(out, a[0], a[1], a[2], a[3], a[4], a[5]);
+  if (num == 1)
+    return inner1(out, a[0], a[1], a[2], a[3], a[4], a[5]);
+  else return -1;
+}