From ab60bb9b8185e8e3c8b398a03a993de950d891cb Mon Sep 17 00:00:00 2001 From: Tim Northover Date: Sun, 2 Nov 2014 01:21:51 +0000 Subject: [PATCH] Docs: update va_arg example with valid x86_64 va_list type. The given example was overflowing its alloca and segfaulting if actually run on x86, so it's a good idea to provide something that works there too. Patch by Ramkumar Ramachandra. llvm-svn: 221077 --- llvm/docs/LangRef.rst | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index ddef803..3b7d80b 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -6884,14 +6884,21 @@ variable argument handling intrinsic functions are used. .. code-block:: llvm + ; This struct is different for every platform. For most platforms, + ; it is merely an i8*. + %struct.va_list = type { i8* } + + ; For Unix x86_64 platforms, va_list is the following struct: + ; %struct.va_list = type { i32, i32, i8*, i8* } + define i32 @test(i32 %X, ...) { ; Initialize variable argument processing - %ap = alloca i8* - %ap2 = bitcast i8** %ap to i8* + %ap = alloca %struct.va_list + %ap2 = bitcast %struct.va_list* %ap to i8* call void @llvm.va_start(i8* %ap2) ; Read a single integer argument - %tmp = va_arg i8** %ap, i32 + %tmp = va_arg i8* %ap2, i32 ; Demonstrate usage of llvm.va_copy and llvm.va_end %aq = alloca i8* -- 2.7.4