[Mesa-dev] [PATCH 3/7] configure.ac: rework llvm libs handling for 3.9+

[Emil Velikov]

On 5 October 2017 at 18:47, Tobias Droste <tdroste at gmx.de> wrote:
> Am Donnerstag, 5. Oktober 2017, 12:19:05 CEST schrieb Emil Velikov:
>> From: Emil Velikov <emil.velikov at collabora.com>
>>
>> Earlier versions need different quirks, but as of LLVM 3.9 llvm-config
>> provides --link-shared/link-static toggles.
>>
>> The output of which seems to be reliable - looking at LLVM 3.9, 4.0 and
>> 5.0.
>>
>> Note that there are earlier code will be used for pre LLVM 3.9 and is
>> unchanged.
>>
>> This effectively fixes LLVM static linking, while providing a clearer
>> and more robust solution for future versions.
>>
>> Mildly interesting side notes:
>>
>>  - build-mode (introduced with 3.8) was buggy with 3.8
>> It shows "static" when build with -DLLVM_LINK_LLVM_DYLIB=ON, yet it was
>> consistent with --libs. The latter shows the static libraries.
>>
>>  - libnames and libfiles are broken with LVM 3.9
>> The library prefix and extension is printed twice liblibLLVM-3.9.so.so
>>
>> Cc: mesa-stable at lists.freedesktop.org
>> Cc: Dieter Nützel <Dieter at nuetzel-hh.de>
>> Cc: Michel Dänzer <michel.daenzer at amd.com>
>> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
>> ---
>>  configure.ac | 29 +++++++++++++++++++----------
>>  1 file changed, 19 insertions(+), 10 deletions(-)
>>
>> diff --git a/configure.ac b/configure.ac
>> index 308938a5a88..dbaa6569e4e 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -2684,18 +2684,27 @@ if test "x$enable_llvm" = xyes; then
>>      dnl this was causing the same libraries to be appear multiple times
>>      dnl in LLVM_LIBS.
>>
>> -    LLVM_LIBS="`$LLVM_CONFIG --libs ${LLVM_COMPONENTS}`"
>> -
>> -    if test "x$enable_llvm_shared_libs" = xyes; then
>> -        if test $LLVM_VERSION_MAJOR -lt 4 -o "`$LLVM_CONFIG --shared-mode ${LLVM_COMPONENTS}`" = static; then
>> -            detect_old_buggy_llvm
>> +    if test $LLVM_VERSION_MAJOR -ge 4 -o $LLVM_VERSION_MAJOR -eq 3 -a $LLVM_VERSION_MINOR -ge 9; then
>> +        if test "x$enable_llvm_shared_libs" = xyes; then
>> +            LLVM_LIBS="`$LLVM_CONFIG --link-shared --libs ${LLVM_COMPONENTS}`"
>> +        else
>> +            LLVM_LIBS="`$LLVM_CONFIG --link-static --libs ${LLVM_COMPONENTS} --system-libs`"
>> +            dnl llvm-config lists the system libs on a separate line. While
>> +            dnl invoking --system-libs without --link-static assumes shared link.
>> +            dnl Everybody now, say - Thank you LLVM developers
>> +            LLVM_LIBS="`echo $LLVM_LIBS | $SED 's/\n//g'`"
>
> Split this into two calls?
>
> LLVM_LIBS="`$LLVM_CONFIG --link-static --libs ${LLVM_COMPONENTS}`"
> dnl We need to link to llvm system libs when using static libs
> LLVM_LIBS="$LLVM_LIBS `$LLVM_CONFIG --link-static --system-libs`"
>
Seems wasteful to invoke llvm-config twice considering it's capable of
doing it in one go. Modulo bugs that is...

> Either way:
> Reviewed-by: Tobias Droste <tdroste at gmx.de>
>
Thanks. Barring any objections, I'll opt for your suggestion but will
keep a comment why.

Invoking llvm-config with both -libs and --system-libs produces the
two separate lines - each for the set of libraries.
Call the program twice, effectively folding them into a single line.

Thanks
Emil