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Python C-library import paths

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  Python C-library import paths Wookey <wookey@wookware.org> - 2022-04-01 03:40 +0200
    Re: Python C-library import paths "M. Zhou" <lumin@debian.org> - 2022-04-01 06:50 +0200
      Re: Python C-library import paths Wookey <wookey@wookware.org> - 2022-04-02 14:00 +0200
        Re: Python C-library import paths Simon McVittie <smcv@debian.org> - 2022-04-02 17:10 +0200
          Re: Python C-library import paths Wookey <wookey@wookware.org> - 2022-04-03 04:40 +0200

#14037 — Python C-library import paths

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I am packaging apache tvm. It builds a C-library libtvm.so (and libtvm_runtime.so).
It also has a python interface which is how most people use it, so I've built that into python3-tvm

It has a /usr/bin/tvmc which fails if you run it due to not being able to find the installed c-libraries.

I have no idea how the python c-library-finding mechanism constructs
its path list, so I'm not sure where to prod this to make it
work. There is presumably a right place to add a path to look on, or
maybe to enable the 'it's in the standard debian system path - just do what /etc/ld.so.conf.d/* says'
functionality.

Currently I get this:
$ tvmc
Traceback (most recent call last):
  File "/usr/bin/tvmc", line 33, in <module>
    sys.exit(load_entry_point('tvm==0.8.0', 'console_scripts', 'tvmc')())
  File "/usr/bin/tvmc", line 25, in importlib_load_entry_point
    return next(matches).load()
  File "/usr/lib/python3.9/importlib/metadata.py", line 77, in load
    module = import_module(match.group('module'))
  File "/usr/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 972, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 972, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 972, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 850, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/usr/lib/python3/dist-packages/tvm/__init__.py", line 26, in <module>
    from ._ffi.base import TVMError, __version__, _RUNTIME_ONLY
  File "/usr/lib/python3/dist-packages/tvm/_ffi/__init__.py", line 28, in <module>
    from .base import register_error
  File "/usr/lib/python3/dist-packages/tvm/_ffi/base.py", line 71, in <module>
    _LIB, _LIB_NAME = _load_lib()
  File "/usr/lib/python3/dist-packages/tvm/_ffi/base.py", line 51, in _load_lib
    lib_path = libinfo.find_lib_path()
  File "/usr/lib/python3/dist-packages/tvm/_ffi/libinfo.py", line 146, in find_lib_path
    raise RuntimeError(message)
RuntimeError: Cannot find the files.
List of candidates:
/home/wookey/bin/libtvm.so
/usr/local/bin/libtvm.so
/usr/bin/libtvm.so
/bin/libtvm.so
/usr/local/games/libtvm.so
/usr/games/libtvm.so
/usr/lib/python3/dist-packages/tvm/libtvm.so
/usr/lib/libtvm.so
/home/wookey/bin/libtvm_runtime.so
/usr/local/bin/libtvm_runtime.so
/usr/bin/libtvm_runtime.so
/bin/libtvm_runtime.so
/usr/local/games/libtvm_runtime.so
/usr/games/libtvm_runtime.so
/usr/lib/python3/dist-packages/tvm/libtvm_runtime.so
/usr/lib/libtvm_runtime.so

So it tries quite hard to find it, but doesn't know about multiarch and thus fails to look in the right place:
/usr/lib/<triplet>/   (/usr/lib/x86_64-linux-gnu/ on this box)

Also does python really think that /usr/local/games/ should be cheked before /usr/lib/ ? That just seems wrong.

Clues about where to prod gratefully received. 

I see that /usr/lib/python3/dist-packages/tvm/_ffi/libinfo.py contains
a function 'get_dll_directories' which looks promising and adds
TVM_LIBRARY_PATH to the search list and if I run tvmc like this:
 TVM_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu/ tvmc
then that path is at the top of the list.

OK, but that mostly reveals a second issue: it's looking for
libtvm.so, but that unversioned link is only provoded in the dev package
libtvm-dev. The library package has the versioned filenames
/usr/lib/x86_64-linux-gnu/libtvm.so.0
/usr/lib/x86_64-linux-gnu/libtvm_runtime.so.0

So I also have to persuade it to look for libtvm.so.0 not
libtvm.so. Where does that info live?  OK, a bit more research shows
that that is in /usr/lib/python3/dist-packages/tvm/_ffi/libinfo.py
which is in the source as python/tvm/_ffi_libinfo.py, in find_lib_path
and that's easy to fix, and probably even the right place to fix it?

The paths is harder though. get_dll_directories in
python/tvm/_ffi_libinfo.py adds $PATH after $LD_LIBRARY_PATH to make
it's search list. Is searching $PATH for libraries ever right?

What it should actually be adding is what's in /etc/ld.so.conf.d/*
That can be listed with
/sbin/ldconfig -v 2>/dev/null | grep -v ^$'\t' | cut -d: -f1
(yuk? is there really no better way?)

How does one do that in python to get that set of path added in the
libinfo.py function?
https://github.com/apache/tvm/blob/main/python/tvm/_ffi/libinfo.py

Am I barking up the right tree here or is there a better way?

Wookey
-- 
Principal hats:  Debian, Wookware, ARM
http://wookware.org/

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#14038

On Fri, 2022-04-01 at 02:32 +0100, Wookey wrote:
> 
> RuntimeError: Cannot find the files.
> List of candidates:
> /home/wookey/bin/libtvm.so
> /usr/local/bin/libtvm.so
> /usr/bin/libtvm.so
> /bin/libtvm.so
> /usr/local/games/libtvm.so
> /usr/games/libtvm.so
> /usr/lib/python3/dist-packages/tvm/libtvm.so
> /usr/lib/libtvm.so
> /home/wookey/bin/libtvm_runtime.so
> /usr/local/bin/libtvm_runtime.so
> /usr/bin/libtvm_runtime.so
> /bin/libtvm_runtime.so
> /usr/local/games/libtvm_runtime.so
> /usr/games/libtvm_runtime.so
> /usr/lib/python3/dist-packages/tvm/libtvm_runtime.so
> /usr/lib/libtvm_runtime.so
> 
> So it tries quite hard to find it, but doesn't know about multiarch
> and thus fails to look in the right place:
> /usr/lib/<triplet>/   (/usr/lib/x86_64-linux-gnu/ on this box)

dlopen should know the multiarch triplet on debian. They have written
their own ffi loader, so I think it is an upstream bug. The upstream
should detect and add multiarch directory to the paths.

> 
> I see that /usr/lib/python3/dist-packages/tvm/_ffi/libinfo.py
> contains
> a function 'get_dll_directories' which looks promising and adds
> TVM_LIBRARY_PATH to the search list and if I run tvmc like this:
>  TVM_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu/ tvmc
> then that path is at the top of the list.

User specified stuff goes first. That makes sense.

> OK, but that mostly reveals a second issue: it's looking for
> libtvm.so, but that unversioned link is only provoded in the dev
> package
> libtvm-dev. The library package has the versioned filenames
> /usr/lib/x86_64-linux-gnu/libtvm.so.0
> /usr/lib/x86_64-linux-gnu/libtvm_runtime.so.0

I think it is fine to let it dlopen the libtvm.so, as it says
itself as some sort of "compiler".

Take pytorch as example, python3-torch has some functionalities
for extending itself with C++. As a result, libtorch-dev is
a dependency of python3-torch.

> So I also have to persuade it to look for libtvm.so.0 not
> libtvm.so. Where does that info live?  OK, a bit more research shows
> that that is in /usr/lib/python3/dist-packages/tvm/_ffi/libinfo.py
> which is in the source as python/tvm/_ffi_libinfo.py, in
> find_lib_path
> and that's easy to fix, and probably even the right place to fix it?

If the upstream's own ffi loader does not look at the SOVERSION,
then it should be designed to work without it.

> The paths is harder though. get_dll_directories in
> python/tvm/_ffi_libinfo.py adds $PATH after $LD_LIBRARY_PATH to make
> it's search list. Is searching $PATH for libraries ever right?
> 
> What it should actually be adding is what's in /etc/ld.so.conf.d/*
> That can be listed with
> /sbin/ldconfig -v 2>/dev/null | grep -v ^$'\t' | cut -d: -f1
> (yuk? is there really no better way?)
> 
> How does one do that in python to get that set of path added in the
> libinfo.py function?
> https://github.com/apache/tvm/blob/main/python/tvm/_ffi/libinfo.py
> 
> Am I barking up the right tree here or is there a better way?
> 

This really looked like an ffi loader bug.

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#14039

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On 2022-04-01 00:30 -0400, M. Zhou wrote:
> On Fri, 2022-04-01 at 02:32 +0100, Wookey wrote:
> > 
> > 
> > So it tries quite hard to find it, but doesn't know about multiarch
> > and thus fails to look in the right place:
> > /usr/lib/<triplet>/   (/usr/lib/x86_64-linux-gnu/ on this box)
> 
> dlopen should know the multiarch triplet on debian. They have written
> their own ffi loader, so I think it is an upstream bug. The upstream
> should detect and add multiarch directory to the paths.

Agreed. I also don't think it should use the $PATH paths for finding
libraries (but maybe upstream have some reason for doing that)

I made this patch but it's debian-specific, using dpkg-architecture.

@@ -48,7 +49,8 @@ def get_dll_directories():
     #   $PREFIX/lib/python3.6/site-packages/tvm/_ffi
     ffi_dir = os.path.dirname(os.path.realpath(os.path.expanduser(__file__)))
     source_dir = os.path.join(ffi_dir, "..", "..", "..")
-    install_lib_dir = os.path.join(ffi_dir, "..", "..", "..", "..")
+    multiarch_name = subprocess.run(['dpkg-architecture', '-q', 'DEB_HOST_MULTIARCH'], stdout=subprocess.PIPE).stdout.decode('utf-8').rstrip()
+    install_lib_dir = os.path.join(ffi_dir, "..", "..", "..", "..", multiarch_name)

(and it took me _ages_ to work out that suprocess.run without that
.rstrip() leaves the trailing newline in the string which stops it
working!)

A correct implemntation really should use the full ldconfig set of search paths.

> > OK, but that mostly reveals a second issue: it's looking for
> > libtvm.so, but that unversioned link is only provoded in the dev
> > package
> > libtvm-dev. The library package has the versioned filenames
> > /usr/lib/x86_64-linux-gnu/libtvm.so.0
> > /usr/lib/x86_64-linux-gnu/libtvm_runtime.so.0
> 
> I think it is fine to let it dlopen the libtvm.so, as it says
> itself as some sort of "compiler".
> 
> Take pytorch as example, python3-torch has some functionalities
> for extending itself with C++. As a result, libtorch-dev is
> a dependency of python3-torch.

OK. I see there is also a find_include_path in libinfo.py so I guess
if it needs the headers too then depending on the -dev package is
indeed correct. I've reverted the change to look for libtvm.so.0.


> > What it should actually be adding is what's in /etc/ld.so.conf.d/*
> > That can be listed with
> > /sbin/ldconfig -v 2>/dev/null | grep -v ^$'\t' | cut -d: -f1
> > (yuk? is there really no better way?)

OK. I tried this, and given that I don't know any python it went better than I expected.
So this code makes an array of paths (as strings) from ldconfig -v output.

However I fell at the last hurble of joining the lib_search_dirs array
to the dll_paths list such that I get one list of all the paths, not a
list where the first entry still has multiple entries. My reading of
the docs says that using extend() instead of append() should merge the
lists, but it isn't for some reason. I made them both strings, rather
than one lot of byte array and one lot of strings, but it still
doesn't work. I'm sure this is trivial to fix for someone who actually
knows some python, hence this mail.

So I get this nice set of paths:
search_dirs [['/usr/lib/x86_64-linux-gnu/libfakeroot:', '/usr/local/lib:', '/lib/x86_64-linux-gnu:', '/usr/lib/x86_64-linux-gnu:', '/lib:', '/usr/lib:']]
which is combined with the other paths to get this incorrect data structure:
dll_path: [['/usr/lib/x86_64-linux-gnu/libfakeroot:', '/usr/local/lib:', '/lib/x86_64-linux-gnu:', '/usr/lib/x86_64-linux-gnu:', '/lib:', '/usr/lib:'], '/usr/lib/python3/dist-packages/tvm/_ffi/..', '/usr/lib/python3/dist-packages/tvm/_ffi/../../../build', '/usr/lib/python3/dist-packages/tvm/_ffi/../../../build/Release', '/usr/lib/python3/dist-packages/tvm/_ffi/../../../lib']

Here is the code:
def get_lib_search_dirs():
    """Get unix library search path from ldconfig -v"""
    # loads of output, only lines starting with / are relevant
    output = subprocess.run(["/sbin/ldconfig","-v"],capture_output=True)
    paths = output.stdout.split(b'\n')
    filtered = []
    for path in paths:
        if path[:1] == b'/':
            filtered.append(path.split()[0].decode())
    return [filtered]

def get_dll_directories():
    """Get the possible dll directories"""
    # NB: This will either be the source directory (if TVM is run
    # inplace) or the install directory (if TVM is installed).
    # An installed TVM's curr_path will look something like:
    #   $PREFIX/lib/python3.6/site-packages/tvm/_ffi
    ffi_dir = os.path.dirname(os.path.realpath(os.path.expanduser(__file__)))
    source_dir = os.path.join(ffi_dir, "..", "..", "..")
    lib_search_dirs = get_lib_search_dirs()
    print ("search_dirs",lib_search_dirs)

    dll_path = []

    if os.environ.get("TVM_LIBRARY_PATH", None):
        dll_path.append(os.environ["TVM_LIBRARY_PATH"])

    if sys.platform.startswith("linux") or sys.platform.startswith("freebsd"):
        dll_path.extend(split_env_var("LD_LIBRARY_PATH", ":"))
        dll_path.extend(lib_search_dirs)
    elif sys.platform.startswith("darwin"):
        dll_path.extend(split_env_var("DYLD_LIBRARY_PATH", ":"))
        dll_path.extend(split_env_var("PATH", ":"))
    elif sys.platform.startswith("win32"):
        dll_path.extend(split_env_var("PATH", ";"))

    # Pip lib directory
    dll_path.append(os.path.join(ffi_dir, ".."))
    # Default cmake build directory
    dll_path.append(os.path.join(source_dir, "build"))
    dll_path.append(os.path.join(source_dir, "build", "Release"))
    # Default make build directory
    dll_path.append(os.path.join(source_dir, "lib"))
    print("dll_path:",dll_path)


If it helps with understanding this is what my changes look like as a patch:

Index: tvm-0.8.0/python/tvm/_ffi/libinfo.py
===================================================================
--- tvm-0.8.0.orig/python/tvm/_ffi/libinfo.py
+++ tvm-0.8.0/python/tvm/_ffi/libinfo.py
@@ -17,6 +17,7 @@
 """Library information."""
 import sys
 import os
+import subprocess
 
 
 def split_env_var(env_var, split):
@@ -40,6 +41,17 @@ def split_env_var(env_var, split):
     return []
 
 
+def get_lib_search_dirs():
+    """Get unix library search path from ldconfig -v"""
+    # loads of output, only lines starting with / are relevant
+    output = subprocess.run(["/sbin/ldconfig","-v"],capture_output=True)
+    paths = output.stdout.split(b'\n')
+    filtered = []
+    for path in paths:
+        if path[:1] == b'/':
+            filtered.append(path.split()[0].decode())
+    return [filtered]
+
 def get_dll_directories():
     """Get the possible dll directories"""
     # NB: This will either be the source directory (if TVM is run
@@ -48,7 +60,8 @@ def get_dll_directories():
     #   $PREFIX/lib/python3.6/site-packages/tvm/_ffi
     ffi_dir = os.path.dirname(os.path.realpath(os.path.expanduser(__file__)))
     source_dir = os.path.join(ffi_dir, "..", "..", "..")
-    install_lib_dir = os.path.join(ffi_dir, "..", "..", "..", "..")
+    lib_search_dirs = get_lib_search_dirs()
+    print ("search_dirs",lib_search_dirs)
 
     dll_path = []
 
@@ -57,7 +70,7 @@ def get_dll_directories():
 
     if sys.platform.startswith("linux") or sys.platform.startswith("freebsd"):
         dll_path.extend(split_env_var("LD_LIBRARY_PATH", ":"))
-        dll_path.extend(split_env_var("PATH", ":"))
+        dll_path.extend(lib_search_dirs)
     elif sys.platform.startswith("darwin"):
         dll_path.extend(split_env_var("DYLD_LIBRARY_PATH", ":"))
         dll_path.extend(split_env_var("PATH", ":"))
@@ -71,8 +84,7 @@ def get_dll_directories():
     dll_path.append(os.path.join(source_dir, "build", "Release"))
     # Default make build directory
     dll_path.append(os.path.join(source_dir, "lib"))
-
-    dll_path.append(install_lib_dir)
+    print("dll_path:",dll_path)
 
     if os.path.isdir(source_dir):
         dll_path.append(os.path.join(source_dir, "web", "dist", "wasm"))



Wookey
-- 
Principal hats:  Debian, Wookware, ARM
http://wookware.org/

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#14040

On Sat, 02 Apr 2022 at 12:55:37 +0100, Wookey wrote:
> On 2022-04-01 00:30 -0400, M. Zhou wrote:
> > They have written
> > their own ffi loader, so I think it is an upstream bug. The upstream
> > should detect and add multiarch directory to the paths.
>
> A correct implemntation really should use the full ldconfig set of search paths.

I think what they should actually be doing on Linux (at least in distro
packages) is taking a step back from all these attempts to reproduce
the system's search path for public shared libraries, and instead doing
this in https://github.com/apache/tvm/blob/main/python/tvm/_ffi/base.py:

    ctypes.CDLL('libtvm.so.0')

which will (ask glibc to) do the correct path search, in something like
99% less code.

Maybe all this complexity is needed on Windows or in a "relocatable"
package, but for a distro package it's completely unnecessary and
sometimes harmful.

> I also don't think it should use the $PATH paths for finding
> libraries (but maybe upstream have some reason for doing that)

I suspect the reason is: on Windows, PATH is the equivalent of Linux PATH,
but it also has a dual role as the equivalent of Linux LD_LIBRARY_PATH.

    smcv

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#14041

On 2022-04-02 16:04 +0100, Simon McVittie wrote:
> On Sat, 02 Apr 2022 at 12:55:37 +0100, Wookey wrote:
> > On 2022-04-01 00:30 -0400, M. Zhou wrote:
> > > They have written
> > > their own ffi loader, so I think it is an upstream bug. The upstream
> > > should detect and add multiarch directory to the paths.
> >
> > A correct implemntation really should use the full ldconfig set of search paths.
> 
> I think what they should actually be doing on Linux (at least in distro
> packages) is taking a step back from all these attempts to reproduce
> the system's search path for public shared libraries, and instead doing
> this in https://github.com/apache/tvm/blob/main/python/tvm/_ffi/base.py:
> 
>     ctypes.CDLL('libtvm.so.0')
> 
> which will (ask glibc to) do the correct path search, in something like
> 99% less code.

Aha. That sounds much more the answer to the query in my original mail
'or is there a way to turn on 'just use the system paths' mode?'.

This does indeed work to load the library without a lot of manual
search-path generation, but it's a bit tricky to use in the existing
codebase which wants the loader function to return both a name and a
path, and with this magic loading, I don't know the path.
_LIB, _LIB_NAME = _load_lib()

The second parameter only seems to be used to determine whether libtvm or libtvm_runtime was loaded. I think I can work round that.

OK. This patch appears to basically work:
-- tvm-0.8.0.orig/python/tvm/_ffi/base.py
+++ tvm-0.8.0/python/tvm/_ffi/base.py
@@ -48,15 +48,21 @@ else:

 def _load_lib():
     """Load libary by searching possible path."""
-    lib_path = libinfo.find_lib_path()
     # The dll search path need to be added explicitly in
     # windows after python 3.8
     if sys.platform.startswith("win32") and sys.version_info >= (3, 8):
         for path in libinfo.get_dll_directories():
             os.add_dll_directory(path)
-    lib = ctypes.CDLL(lib_path[0], ctypes.RTLD_GLOBAL)
+
+    use_runtime = os.environ.get("TVM_USE_RUNTIME_LIB", False)
+    if use_runtime:
+        lib = ctypes.CDLL('libtvm_runtime.so.0', ctypes.RTLD_GLOBAL)
+        sys.stderr.write("Loading runtime library %s... exec only\n" % lib._name)
+        sys.stderr.flush()
+    else:
+        lib = ctypes.CDLL('libtvm.so.0', ctypes.RTLD_GLOBAL)
     lib.TVMGetLastError.restype = ctypes.c_char_p
-    return lib, os.path.basename(lib_path[0])
+    return lib

try:
@@ -68,10 +74,10 @@ except ImportError:
 # version number
 __version__ = libinfo.__version__
 # library instance
-_LIB, _LIB_NAME = _load_lib()
+_LIB = _load_lib()

 # Whether we are runtime only
-_RUNTIME_ONLY = "runtime" in _LIB_NAME
+_RUNTIME_ONLY = "runtime" in _LIB._name

Yay!

_Unless_ you ask to use the runtime version - then it blows up.
$ TVM_USE_RUNTIME_LIB=1 tvmc
...
  File "/usr/lib/python3/dist-packages/tvm/auto_scheduler/cost_model/cost_model.py", line 37, in __init__
    self.__init_handle_by_constructor__(_ffi_api.RandomModel)
AttributeError: module 'tvm.auto_scheduler._ffi_api' has no attribute 'RandomModel'

I've not looked into that yet.

Back to the issue of getting the path of the loaded library. Which I no longer obviously _need_, but I would like to know how to do it.

There is ctypes.util.find_library(name) which says it returns a path but
ctypes.util.find_library('tvm')
just returns 
'libtvm.so.0'

I can't see an attribute in the returned lib object to get the path:
lib=ctypes.CDLL('libtvm.so.0')
>>> print(lib)
<CDLL 'libtvm.so.0', handle 1409040 at 0x7f5f0ef48e20>
>> print(lib.__dir__())
['_name', '_FuncPtr', '_handle', '__module__', '__doc__', '_func_flags_', '_func_restype_', '__init__', '__repr__', '__getattr__', '__getitem__', '__dict__', '__weakref__', '__hash__', '__str__', '__getattribute__', '__setattr__', '__delattr__', '__lt__', '__le__', '__eq__', '__ne__', '__gt__', '__ge__', '__new__', '__reduce_ex__', '__reduce__', '__subclasshook__', '__init_subclass__', '__format__', '__sizeof__', '__dir__', '__class__']

But _something_ knows, because if I ask for an incorrect thing it prints it out as an 'AtributeError':
>>> print(lib.wibble)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.9/ctypes/__init__.py", line 387, in __getattr__
    func = self.__getitem__(name)
  File "/usr/lib/python3.9/ctypes/__init__.py", line 392, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: /usr/lib/x86_64-linux-gnu/libtvm.so.0: undefined symbol: wibble

Again, my weak python-foo is holding me back here.


Also, you suggest that for a disto package we just need to do
lib = ctypes.CDLL('libtvm.so.0', ctypes.RTLD_GLOBAL) and scrap 99% of the
code.  However, some of the complicated logic in the special _load_lib
code seems like maybe it shouldn't be thrown away.  Like allowing to
override the path with TVM_LIBRARY_PATH envvar, and setting
TVM_USE_RUNTIME_LIB to load libtvm_runtime rather than libtvm (I've
currently preserved the latter but not the former).

I don't know why this is useful, but I assume upstream has reasons.

I guess I should wave my patches upstream and see what they have to say about all this.

> Maybe all this complexity is needed on Windows or in a "relocatable"
> package, but for a distro package it's completely unnecessary and
> sometimes harmful.

Agreed. Although of course upstreams often want to support all sorts
of 'local install' type circumstances so they have the code anyway,
and we end up maintaining a patch to throw it all away and do
something sensible instead.

> > I also don't think it should use the $PATH paths for finding
> > libraries (but maybe upstream have some reason for doing that)
> 
> I suspect the reason is: on Windows, PATH is the equivalent of Linux PATH,
> but it also has a dual role as the equivalent of Linux LD_LIBRARY_PATH.

That would make sense except the relevant code is already conditional by OS:

if sys.platform.startswith("linux") or sys.platform.startswith("freebsd"):
        dll_path.extend(split_env_var("LD_LIBRARY_PATH", ":"))
        dll_path.extend(split_env_var("PATH", ":"))
    elif sys.platform.startswith("darwin"):
        dll_path.extend(split_env_var("DYLD_LIBRARY_PATH", ":"))
        dll_path.extend(split_env_var("PATH", ":"))
    elif sys.platform.startswith("win32"):
        dll_path.extend(split_env_var("PATH", ";"))

So I think it's actually just wrong. I'll take it upstream.

Wookey
-- 
Principal hats:  Debian, Wookware, ARM
http://wookware.org/

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