Building with support for lCU breaks other Boost libs (e.g. Boost.FileSystem)

[DenizThatMenace]

When building the latest Boost releases (starting with Boost 1.70.0) and enabling support for ICU Boost.Build first warns about an incompatible setting and later fails while compiling Boost.FileSystem because of different settings regarding support for ICU:

 Performing configuration checks

     - default address-model    : 64-bit
     - default architecture     : x86
     - C++11 mutex              : yes
     ...
     - has_icu builds           : yes
 warning: non-free usage requirements <runtime-link>shared ignored
 warning: in main-target icu_options at libs/regex/build/Jamfile.v2:97
     ...
     - iconv (libc)             : yes
     - icu                      : yes
     - native-atomic-int32-supported : yes
     ...
     ...
 error: Name clash for '<p/home/jenkins/workspace/Pipeline_Boost-1.71.0/gcc8/installed/opt/some/path/lib/x86_64-linux-gnu>libboost_filesystem-gcc8-mt-x64-1_71.so.1.71.0'
 error: 
 error: Tried to build the target twice, with property sets having 
 error: these incompatible properties:
 error: 
 error:     -  none
 error:     -  <dll-path>/opt/some/path/bin <linkflags>-L/opt/some/path/lib/x86_64-linux-gnu <linkflags>-licudata <linkflags>-licui18n <linkflags>-licuuc
 error: 
 error: Please make sure to have consistent requirements for these 
 error: properties everywhere in your project, especially for install
 error: targets.

The warning points to line 97 in libs/regex/build/Jamfile.v2which seems problematic.
And indeed, if I patch that file to never enable support for ICU in Boost.Regex building all of Boost succeeds.

Of course, this is not a solution, because I wanted ICU support compiled in. But it seems to have proven that the Jamfile of Boost.Regex somehow seems to be broken or at least incompatible.

---

For the sake of completeness, I used the following command when trying to build Boost:

b2 -j4 -q \
  --build-dir=/home/jenkins/workspace/Pipeline_Boost-1.71.0/gcc8/build/boost \
  --build-type=minimal \
  --layout=versioned \
  address-model=64 \
  install \
  --prefix=/home/jenkins/workspace/Pipeline_Boost-1.71.0/gcc8/installed/opt/some/path \
  --libdir=/home/jenkins/workspace/Pipeline_Boost-1.71.0/gcc8/installed/opt/some/path/lib/x86_64-linux-gnu \
  --cmakedir=/home/jenkins/workspace/Pipeline_Boost-1.71.0/gcc8/installed/opt/some/path/share/boost \
  dll-path=/opt/some/path/lib/x86_64-linux-gnu \
  -sICU_PATH="/opt/some/path" \
  -sICU_LINK="-L/opt/some/path/lib/x86_64-linux-gnu -licuuc -licudata -licui18n" \
  toolset=gcc-8 \
  cflags="-m64 -fpic -fdiagnostics-color=always -O3 -g" \
  cxxflags="-m64 -fpic -fdiagnostics-color=always -O3 -g -std=c++17" \
  linkflags="-Wl,--as-needed"

The ICU libs that should be used are in the denoted location under /opt/some/path/lib/x86_64-linux-gnu.

[jzmaddock]

I can reproduce this, reduced command line is:

./b2  -sICU_PATH="/opt/some/path"   -sICU_LINK="-L/opt/some/path/lib/x86_64-linux-gnu -licuuc -licudata -licui18n"   toolset=gcc-8 -n

However, I suspect Boost.Regex is a bystander here, if I add --with-regex --with-filesystem to the command line then everything builds fine, the culprit appears to be Boost.Log, because the minimal reproducer is:

./b2  -sICU_PATH="/opt/some/path"   -sICU_LINK="-L/opt/some/path/lib/x86_64-linux-gnu -licuuc -licudata -licui18n"   toolset=gcc-8 -n --with-filesystem  --with-log

In any case we will need a Boost.Build expert to solve this one!

[Lastique]

I'm not an expert in Boost.Build but it seems that Boost.Log triggers the problem because it depends (by default) both on Boost.Regex and a few other Boost libraries, like Filesystem, DateTime, Thread, etc. It is those other dependent libraries are randomly mentioned in the error message, sometimes different from one run to another, depending on which ones are specified in the command line.

It seems like Boost.Build doesn't propagate <linkflags> to some of Boost.Log dependent libraries, which are left to build both with the custom <linkflags> and without. I don't see what I can do about it in Boost.Log. Looks like a Boost.Build issue to me.

[pdimov]

Since it looks like Boost.Regex will add -licuuc -licudata -licui18n by itself if ICU_LINK is not specified, you can try omitting it, or if -L/opt/some/path/lib/x86_64-linux-gnu is required, try adding it via linkflags=-L/opt/some/path/lib/x86_64-linux-gnu instead of ICU_LINK.

[pdimov]

It seems like Boost.Build doesn't propagate <linkflags> to some of Boost.Log dependent libraries

The problem is the opposite; that it does propagate it. Log inherits the <linkflags> from Regex and passes it down to Filesystem, but the other copy of Filesystem (requested via --with-filesystem) doesn't have the <linkflags> because it doesn't depend on Regex from which to get them.

[Lastique]

I'm assuming every target should have the same linkflags, regardless whether it uses ICU or not. Indeed, some linker flags need to be applied to every linking target.

From Steven's response on the ML it sounds like --with-filesystem creates a new root and a separate dependency tree, which does not have linkflags and hence we have a problem. My understanding was that there is only one root and only one dependency tree during the build, and --with-* flags only whitelist some parts of the tree. I still think this would probably make more sense and would solve the problem, but I understand this might be a difficult change.

Regarding using linkflags instead of variables, the latter are documented as the interface for customizing ICU location. The docs will need to be updated.

[DenizThatMenace]

I can confirm that building boost succeeds when omitting the ICU_LINK option and instead providing the linker-search-path via linkflags=-L/opt/some/path/lib/x86_64-linux-gnu, as @pdimov described above.

If this is the desired solution, the documentation should indeed be changed as @Lastique already suggested.

[pdimov]

Creating a single root has at least two disadvantages I can think of; first, each library's usage requirements will propagate to every other, regardless of whether that other is a dependency. That is, at the moment Boost.Regex affects Filesystem through Log, with a single root it will affect all. Second, b2 --with-filesystem and b2 --with-filesystem --with-log will still use different options for Filesystem.

It seems to me that Regex shouldn't be setting <linkflags> in a usage requirement. Instead, there should be a mechanism to add that -L to <search> of the appropriate ICU lib targets. Although I can guess why things are done this way - the library names may well need to be customized on some oddball configuration.

[Lastique]

For static libraries one has to propagate -l and -L to the dependent targets. Though it only needs to propagate upwards but not downwards (i.e. from Regex to Log, but not from Log to Filesystem).

[pdimov]

This should happen automatically when using lib, as is the case here when ICU_LINK isn't set.

[jzmaddock]

Clearly I will fix this in whatever way will work.

If all you need is to set custom include and library search paths then using include= and linkflags= on the command line will suffice (I hope - do we need dll-path as well?). The main use case for ICU_LINK is to set the linker command line in cases where the names of the ICU libraries are non-standard. ICU has form here in that the names have changed at least once, are already different on windows and linux (anywhere else?) and between debug and static link versions.

Suggested changes and improvements welcome. Otherwise I don't really know what to do to fix this.

[pdimov]

I don't really know how this should be handled in an idiomatic Boost.Build manner; maybe @swatanabe knows and hasn't switched off his notifications.

What I would do here is try to use the built-in lib as in the branch when ICU_LINK isn't set, but provide name override variables for each ICU library. Something like ICU_NAME_ICUUC, ICU_NAME_ICUDT, ICU_NAME_ICUIN (or perhaps ICU_ICUUC_NAME? or just ICUUC_NAME? not sure.)

For the libpath, either a common ICU_LIBPATH or per-library ones, then add those in <search> instead of, or in addition to, the current default.

Not sure about the dll-path.

[pdimov]

I suppose the "right" way to do it is to add icu.jam to the Boost.Build tools, along the lines of the existing https://github.com/boostorg/build/blob/develop/src/tools/zstd.jam or https://github.com/boostorg/build/blob/develop/src/tools/openssl.jam.

[swatanabe]

AMDG

On 10/15/19 12:01 PM, Peter Dimov wrote:

I suppose the "right" way to do it is to add icu.jam to the Boost.Build tools, along the lines of the existing https://github.com/boostorg/build/blob/develop/src/tools/zstd.jam or https://github.com/boostorg/build/blob/develop/src/tools/openssl.jam.

A bit more digging, shows that the problem is not copying the file. Otherwise there are lots of other properties that would cause problems. The actual cause is that stage relinks executables and libraries when their dll-path properties change. That's why only the options that affect the linker show up in the error.

I don't think that making icu.jam will actually help with this problem. If you need to set rpath on boost_regex.so, there's currently no good way to achieve it without using dll-path in the usage-requirements which is what triggers this error in the first place.

The problem could be avoided if boost-install.jam didn't use on and instead only directly added libraries that have no corresponding stage target, but that'll be quite a pain to implement.

In Christ, Steven Watanabe

[pdimov]

Thanks Steven.

So the problem is that we need to pass <dll-path> to the install rule, and the only way to do it via usage requirements, which breaks.

This problem is actually not introduced by the commit adding <install-dependencies>on to the stage target, because the install target already had it, as package.install adds <install-dependencies>on. (https://github.com/boostorg/boost_install/blob/develop/boost-install.jam#L983 https://github.com/boostorg/build/blob/develop/src/tools/package.jam#L237)

Am I right in thinking that the correct fix here is to add a "requirements" parameter to boost-install, which should then be passed to package.install and install? This will allow Regex to do

boost-install boost_regex : <dll-path>$(ICU_DLLPATH) ;

instead of putting the dll-path in a usage requirement.

[pdimov]

Update: what I suggested above doesn't work. When I implement it, the result is

error: Name clash for '<p/home/pdimov/.local/lib>libboost_regex.so.1.72.0'
error: 
error: Tried to build the target twice, with property sets having 
error: these incompatible properties:
error: 
error:     -  none
error:     -  <dll-path>/opt/testpath/bin
error: 
error: Please make sure to have consistent requirements for these 
error: properties everywhere in your project, especially for install
error: targets.

That's presumably because libboost_regex.so installed by Regex has the <dll-path> and the one indirectly installed by Log via <install-dependencies>on does not. :-/

I don't have any better ideas at this point.

For reference, the changes I tried are https://github.com/boostorg/boost_install/commit/3ebce827724f481269af9769adf393e1d36c52ca, https://github.com/boostorg/boost/commit/f5fecfc1dca4a3f517804e7d270017732e5b8738, https://github.com/boostorg/regex/commit/1dc5c2641388ca5eafee4b313b059371e0f68b4d.

[jzmaddock]

I've confirmed I can fix this by removing the dll-path property when ICI_LINK is set.

Or I can fix by using macros to define possible custom names for the ICU libraries.

The latter looks cleaner to me, but in the process of documenting this, I ran into another issue:

What is the correct way to tell b2 where to look for external libraries?

If I use

b2 search=/opt/some/path

Then almost nothing gets built (only log and locale as far as I can see), should this not work? And should "search" be a documented feature?

Alternatively

b2 linkflags=-L/opt/some/path

Add the options to the end of the command line (after all the object files) which I assume means that the library path will not be used when resolving symbols from those files? Or am I misunderstanding the -L option? I confess I can never remember which options are order specific :(

[pdimov]

I think that the right feature for setting the global library path is <library-path>. <search> is only meaningful as a requirement for lib.

[pdimov]

Either <conditional>@path_options or <search>$(ICU_PATH)/bin <search>$(ICU_PATH)/lib (or perhaps just use <search>$(ICU_PATH)/bin <search>$(ICU_PATH)/lib <search>$(ICU_PATH)/bin64 <search>$(ICU_PATH)/lib64 everywhere) probably still needs to be given to lib even when the names are overridden.