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Fix symlink collision bug #3

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Fix symlink collision bug #3

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22 changes: 19 additions & 3 deletions pkg_config.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,9 @@ def _find_binary(ctx, binary_name):
return _success(binary)

def _execute(ctx, binary, args):
result = ctx.execute([binary] + args)
result = ctx.execute(
[binary] + args,
)
if result.return_code != 0:
return _error("Failed execute {} {}".format(binary, args))
return _success(result.stdout)
Expand Down Expand Up @@ -86,15 +88,28 @@ def _ignore_opts(opts, ignore_opts):
remain += [opt]
return remain

def _symlink_no_duplicate(ctx, src, dest):
if not dest.exists:
ctx.symlink(src, dest)
return True
return False

def _symlinks(ctx, basename, srcpaths):
result = []
root = ctx.path("")
base = root.get_child(basename)
rootlen = len(str(base)) - len(basename)
for src in [ctx.path(p) for p in srcpaths]:
dest = base.get_child(src.basename)
ctx.symlink(src, dest)
result += [str(dest)[rootlen:]]
# if the directory already exists then:
# 1) attempt to modify the name with the parent directory name
# 2) if that fails don't create the symlink at all
# we can sometimes skip symlink creation because of ocassional
# duplicates in pkg_config output
if dest.exists:
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Instead of just looking up 1 level in the directory tree, what do you think about generating unique identifiers from the complete srcpath? (For example: s.replace("_", "__").replace("/", "_slash_")?) This will be more robust to collisions in file paths.

dest = base.get_child(src.basename + src.dirname.basename)
if _symlink_no_duplicate(ctx, src, dest):
result += [str(dest)[rootlen:]]
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Modifying the name of the symlink that is created like this may lead to nondeterministic include path naming (or spooky action at a distance, where include path names depend on the order in which symlinks are created). Moreover, if you look at how the return value of _symlinks is used, you should see that this changes how the strip_include option to the pkg_config rule works.

For example, consider a package with include paths /usr/include/x86_64-linux-gnu/MyPackage and /usr/include/MyPackage. It provides the include files /usr/include/x86_64-linux-gnu/MyPackage/my.h and /usr/include/MyPackage/package.h.

A user of the pkg_config Bazel rule might specify a strip_prefix value of MyPackage, so that they can just #include "my.h" and #include "package.h" directly.

Under this PR, Bazel will create symlinks named includes/MyPackage and includes/include/MyPackage or includes/x86_64-linux-gnu/MyPackage, depending on which gets created first. There is no single strip_prefix value that can correctly strip out both of these. Furthermore, the names of the symlinks that get created depends on the order in which they are created, which is undesirable for multiple reasons.

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yes, that makes a lot of sense; a strip_prefix or prefix (for adding a path prefix)

return result

def _deps(ctx, pkg_config, pkg_name):
Expand Down Expand Up @@ -192,3 +207,4 @@ pkg_config = repository_rule(
local = True,
implementation = _pkg_config_impl,
)