01/06: gnu: llvm, clang: Update to 6.0.0.

[Mark H Weaver]

Hi Marius,

mbakke pushed a commit to branch master
in repository guix.
commit 9bdbabe963e48bcac11c053a38d990873ca48dca
Date: Sat Mar 31 22:04:44 2018 +0200
gnu: llvm, clang: Update to 6.0.0.

Thanks for this, but ...

+ ;; Link to libclang_rt files from clang-runtime.
+ ;; This substitution needed slight adjustment in 3.8.
+ (if (< 3.8 (string->number ,(version-major+minor
+ (package-version
+ clang-runtime))))
+ (substitute* "lib/Driver/Tools.cpp"
+ (("TC\\.getDriver\\(\\)\\.ResourceDir")
+ (string-append "\"" compiler-rt "\"")))
+ (substitute* "lib/Driver/ToolChain.cpp"
+ (("getDriver\\(\\)\\.ResourceDir")
+ (string-append "\"" compiler-rt "\""))))

The version comparison code above is incorrect. This code will judge
version 3.10 to be older than 3.8.

'string->number' is never a sensible procedure to apply to version
numbers with more than one component, because it is not injective, let
alone order-preserving. For example, "3.1" and "3.10" map to the same
number 3.1, although they are different versions.

I suggest that you use 'version-compare', 'version>?', or 'version>=?'
from (guix utils). Note that these are not available to build-side
code, so the entire 'if' should be lifted to client-side code, which is
better anyway. Maybe something like this (untested):

;; Link to libclang_rt files from clang-runtime.
;; This substitution needed slight adjustment in 3.8.
,(let ((runtime-version (version-major+minor
(package-version
clang-runtime))))
(if (version>? runtime-version "3.8")
'(substitute* "lib/Driver/Tools.cpp"
(("TC\\.getDriver\\(\\)\\.ResourceDir")
(string-append "\"" compiler-rt "\"")))
'(substitute* "lib/Driver/ToolChain.cpp"
(("getDriver\\(\\)\\.ResourceDir")
(string-append "\"" compiler-rt "\"")))))

What do you think?

Mark