[lld] r276574 - Make readExpr return an Expr object instead of a vector of tokens.

[Davide Italiano via llvm-commits]

On Sun, Jul 24, 2016 at 11:19 AM, Rui Ueyama via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: ruiu
> Date: Sun Jul 24 13:19:40 2016
> New Revision: 276574
>
> URL: http://llvm.org/viewvc/llvm-project?rev=276574&view=rev
> Log:
> Make readExpr return an Expr object instead of a vector of tokens.
>
> Previously, we handled an expression as a vector of tokens. In other
> words, an expression was a vector of uncooked raw StringRefs.
> When we need a value of an expression, we used ExprParser to run
> the expression.
>
> The separation was needed essentially because parse time is too
> early to evaluate an expression. In order to evaluate an expression,
> we need to finalize section sizes. Because linker script parsing
> is done at very early stage of the linking process, we can't
> evaluate expressions while parsing.
>
> The above mechanism worked fairly well, but there were a few
> drawbacks.
>
> One thing is that we sometimes have to parse the same expression
> more than once in order to find the end of the expression.
> In some contexts, linker script expressions have no clear end marker.
> So, we needed to recognize balanced expressions and ternary operators.
>
> The other is poor error reporting. Since expressions are parsed
> basically twice, and some information that is available at the first
> stage is lost in the second stage, it was hard to print out
> apprpriate error messages.
>
> This patch fixes the issues with a new approach.
>
> Now the expression parsing is integrated into ScriptParser.
> ExprParser class is removed. Expressions are represented as lambdas
> instead of vectors of tokens. Lambdas captures information they
> need to run themselves when they are created.
>
> In this way, ends of expressions are naturally detected, and
> errors are handled in the usual way. This patch also reduces
> the amount of code.
>
> Differential Revision: https://reviews.llvm.org/D22728
>

This commit breaks (at least) this case. Can you please take a look?

[davide at ganondorf bin]$ ./ld.lld reduction.script
line 3: malformed number: kernbase
  . = kernbase + kernphys + SIZEOF_HEADERS;
      ^
[davide at ganondorf bin]$ cat reduction.script
SECTIONS
{
  . = kernbase + kernphys + SIZEOF_HEADERS;
}

--
Davide