Use architecture-specific va_list type

Previously, cproc effectively used used

	typedef struct { /* 32 bytes, 8-byte aligned */ } __builtin_va_list[1];

However, this is not quite correct for x86_64 nor aarch64, though
it was close enough for both to work in most cases.

In actuality, for x86_64 we want

	typedef struct { /* 24 bytes, 8-byte aligned */ } __builtin_va_list[1];

and for aarch64 we want

	typedef struct { /* 32 bytes, 8-byte aligned */ } __builtin_va_list;

The difference only appears when the size of va_list matters, or
when va_list is passed as a parameter. However, the former is not
often the case, and the aarch64 ABI replaces aggregate arguments
with pointers to caller-allocated memory, which is quite similar
to arrays decaying to pointers in C except that the struct is not
copied.

Additionally, riscv64 simply uses

	typedef void *__builtin_va_list;

which again has a different size and calling convention.

To fix this, make the __builtin_va_list type architecture-specific
and use architecture-specific tests for varargs-related functionality.

1 files changed, 4 insertions, 1 deletions

diff --git a/scope.c b/scope.c
index 72025f5..c116670 100644
--- a/scope.c
+++ b/scope.c
@@ -25,13 +25,16 @@ scopeinit(void)
 		{"__builtin_va_arg",     {.kind = DECLBUILTIN, .builtin = BUILTINVAARG}},
 		{"__builtin_va_copy",    {.kind = DECLBUILTIN, .builtin = BUILTINVACOPY}},
 		{"__builtin_va_end",     {.kind = DECLBUILTIN, .builtin = BUILTINVAEND}},
-		{"__builtin_va_list",    {.kind = DECLTYPE, .type = &typevalist}},
 		{"__builtin_va_start",   {.kind = DECLBUILTIN, .builtin = BUILTINVASTART}},
 	};
+	static struct decl valist;
 	struct builtin *b;
 
 	for (b = builtins; b < builtins + LEN(builtins); ++b)
 		scopeputdecl(&filescope, b->name, &b->decl);
+	valist.kind = DECLTYPE;
+	valist.type = targ->typevalist;
+	scopeputdecl(&filescope, "__builtin_va_list", &valist);
 }
 
 struct scope *