[llvm-dev] Zero-sized globals in LLVM IR

[Manuel Jacob via llvm-dev]

How did you come to the conclusion that a zero-length array generates 
something of at least of size 1?  I don't see a significant difference 
between the assembly output of "@a1 = global [0 x i8] []" and "@a2 = 
global {} {}".

	.type	a1, at object              # @a1
	.data
	.globl	a1
a1:
	.size	a1, 0

	.type	a2, at object              # @a2
	.bss
	.globl	a2
	.p2align	3
a2:
	.size	a2, 0

Subjectively, I'd consider "@a2 = global {} {}" to be the "idiomatic" 
way to define a zero-sized global.  IMHO it shouldn't trigger an 
assertion.

On 2018-07-17 12:58, David Chisnall via llvm-dev wrote:
> Hello the list,
> 
> What is the correct type for a global of size zero?  I need the
> compiler to be able to generate one, so that the linker will insert it
> at a specific position without perturbing the location of anything
> else in the section.  I have tried a zero-length array (generates
> something at least one byte).  At Nuno’s suggestion, I tried a
> structure with no fields.  In release builds, this works correctly,
> but in debug builds it triggers an assertion that the type must be
> sized.
> 
> What is the recommended way of doing this?
> 
> David
> 
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