Revert "Add support for variadic arguments in generated stubs"

This reverts commit d27bb543.

Reason for revert: This CL causes HW encoding functionality loss on some Chrome OS devices, minnie and kevin.

Original change's description:
> Add support for variadic arguments in generated stubs
>
> Previously we were using va_list for variadic arguments. The downside
> for this was that only the first value from the variadic argument was
> passed to the original function.
>
> To make it work properly we have to use the __VA_ARGS__ variadic macro
> that was introduces in C99 and is available in all major C/C++
> compilers.
>
> Change-Id: I50652f7348a16214811aaab8af116d78cdb70444
> Reviewed-on: https://chromium-review.googlesource.com/c/1323089
> Reviewed-by: Patrik Höglund <phoglund@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Commit-Queue: Tomáš Popela <tomas.popela@gmail.com>
> Cr-Commit-Position: refs/heads/master@{#606588}

TBR=phoglund@chromium.org,dpranke@chromium.org,braveyao@chromium.org,brucedawson@chromium.org,tomas.popela@gmail.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 904586
Change-Id: I04157ea305decc170d5efd4ba228c92bd4020ef6
Reviewed-on: https://chromium-review.googlesource.com/c/1333013
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607545}

tools/generate_stubs/generate_stubs.py

@@ -17,6 +17,16 @@ or a header + implementation file of stubs suitable for use in a POSIX system.
 
 This script also handles variadic functions, e.g.
 void printf(const char* s, ...);
+
+TODO(hclam): Fix the situation for variadic functions.
+Stub for the above function will be generated and inside the stub function it
+is translated to:
+void printf(const char* s, ...) {
+  printf_ptr(s, (void*)arg1);
+}
+
+Only one argument from the variadic arguments is used and it will be used as
+type void*.
 """
 
 __author__ = 'ajwong@chromium.org (Albert J. Wong)'
@@ -101,9 +111,11 @@ STUB_FUNCTION_DEFINITION = (
 VARIADIC_STUB_FUNCTION_DEFINITION = (
     """extern %(return_type)s %(name)s(%(params)s) __attribute__((weak));
 %(return_type)s %(export)s %(name)s(%(params)s) {
-#define %(name)s_ptr_variadic(%(arg_list)s, ...) \
-%(name)s_ptr(%(arg_list)s, ##__VA_ARGS__)
-  return %(name)s_ptr_variadic(%(arg_list)s);
+  va_list args___;
+  va_start(args___, %(last_named_arg)s);
+  %(return_type)s ret___ = %(name)s_ptr(%(arg_list)s, va_arg(args___, void*));
+  va_end(args___);
+  return ret___;
 }""")
 
 # Template for generating a variadic stub function definition without
@@ -120,9 +132,10 @@ VARIADIC_STUB_FUNCTION_DEFINITION = (
 VOID_VARIADIC_STUB_FUNCTION_DEFINITION = (
     """extern void %(name)s(%(params)s) __attribute__((weak));
 void %(export)s %(name)s(%(params)s) {
-#define %(name)s_ptr_variadic(%(arg_list)s, ...) \
-%(name)s_ptr(%(arg_list)s, ##__VA_ARGS__)
-  %(name)s_ptr_variadic(%(arg_list)s);
+  va_list args___;
+  va_start(args___, %(last_named_arg)s);
+  %(name)s_ptr(%(arg_list)s, va_arg(args___, void*));
+  va_end(args___);
 }""")
 
 # Template for the preamble for the stub header file with the header guards,

tools/generate_stubs/generate_stubs_unittest.py

@@ -42,8 +42,6 @@ SIMPLE_SIGNATURES = [
     ('int corge(void);', _MakeSignature('int', 'corge', ['void'])),
     ('int ferda(char **argv[]);',
      _MakeSignature('int', 'ferda', ['char **argv[]'])),
-    ('void brouk(char *pytlik, ...);',
-     _MakeSignature('void', 'brouk', ['char *pytlik', '...'])),
     ]
 
 TRICKY_SIGNATURES = [
@@ -223,14 +221,6 @@ int  ferda(char **argv[]) {
   return ferda_ptr(argv);
 }""", gs.PosixStubWriter.StubFunction(SIMPLE_SIGNATURES[6][1]))
 
-    # Test variadic argument
-    self.assertEqual("""extern void brouk(char *pytlik, ...) \
-__attribute__((weak));
-void  brouk(char *pytlik, ...) {
-#define brouk_ptr_variadic(pytlik, ...) brouk_ptr(pytlik, ##__VA_ARGS__)
-  brouk_ptr_variadic(pytlik);
-}""", gs.PosixStubWriter.StubFunction(SIMPLE_SIGNATURES[7][1]))
-
   def testWriteImplemenationContents(self):
     outfile = StringIO.StringIO()
     self.writer.WriteImplementationContents('my_namespace', outfile)