llvm dev - Aug 2004 - [LLVMdev] What's the meaning of [0 x sbyte*]?

Hi

When I compiled sendmail v8.11.6 with LLVM 1.2, I found some variables with 
strange type, such as: 
%sys_errlist = external constant [0 x sbyte*]           ; <[0 x sbyte*]*>
[#uses=3]

%tmp.24 = getelementptr [0 x sbyte*]* %sys_errlist, long 0, long %tmp.23        
; <sbyte**> [#uses=1]

The process of getting these is:
1. entry sendmail-8.11.6 directory
2. make CC="/cfrontend/x86/llvm-gcc/bin/gcc"
3. entry obj.Linux.2.4.20-8.i686/sendmail
4. llvm-dis sendmail.bc &> sendmail.ins
5. grep "\[0 x sbyte*\]" sendmail.ins

What is the meaning of [0 x sbyte*]?
A pointer with the type of [0 x sbyte*]* is a void pointer? 

Xia

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On Tue, 17 Aug 2004, [gb2312] ��һ�� wrote:
> When I compiled sendmail v8.11.6 with LLVM 1.2, I found some variables with
> strange type, such as:
> %sys_errlist = external constant [0 x sbyte*]           ; <[0 x
sbyte*]*> [#uses=3]
>
> %tmp.24 = getelementptr [0 x sbyte*]* %sys_errlist, long 0, long %tmp.23   
; <sbyte**> [#uses=1]
> What is the meaning of [0 x sbyte*]?
> A pointer with the type of [0 x sbyte*]* is a void pointer?
Zero length arrays for globals usually occur when the source program
contains something like this:

extern int X[];

Because we don't know the length of X, we give it an LLVM type of [0 x int].

When the linker resolves X with it's definition, it should change to the
correct length.  sys_errlist is defined by libc, which is why you're not
seeing a definition.

Hope this helps,

-Chris

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