Never append to library path in root executable

[guitargeek]

This follows up on 26d24de, where it was made sure that ROOT executables always set the required RPATHs to the ROOT libraries, unless the user disables it with CMAKE_SKIP_INSTALL_RPATH at build time.

Therefore, the code path to set the LD_LIBRARY_PATH in the root executable was still kept for the case where CMAKE_SKIP_INSTALL_RPATH was enabled.

However, when thinking about it further, this is not required. The reason to set CMAKE_SKIP_INSTALL_RPATH is usually because ROOT is intended to be installed into directories that are already in the paths, like in the MacPorts configuration. So if the user doesn't need rpaths, they also don't need ROOT to figure out its library paths.

Therefore, this commit suggests so simply never set the library path in the root executable.

Closes https://its.cern.ch/jira/browse/ROOT-9758

[ferdymercury]

Thanks! Is the Dlopen trick in TUnixSystem still needed?

root/core/unix/src/TUnixSystem.cxx

Lines 4625 to 4650 in f28225c

	#if defined(R__WINGCC) || defined(R__MACOSX)
	if (!dynpath.EndsWith(":")) dynpath += ":";
	dynpath += "/usr/local/lib:/usr/X11R6/lib:/usr/lib:/lib:";
	dynpath += "/lib/x86_64-linux-gnu:/usr/local/lib64:/usr/lib64:/lib64:";
	#else
	// trick to get the system search path
	std::string cmd("LD_DEBUG=libs LD_PRELOAD=DOESNOTEXIST ls 2>&1");
	FILE *pf = popen(cmd.c_str (), "r");
	std::string result = "";
	char buffer[128];
	while (!feof(pf)) {
	if (fgets(buffer, 128, pf) != NULL)
	result += buffer;
	}
	pclose(pf);
	std::size_t from = result.find("search path=", result.find("(LD_LIBRARY_PATH)"));
	std::size_t to = result.find("(system search path)");
	if (from != std::string::npos && to != std::string::npos) {
	from += 12;
	std::string sys_path = result.substr(from, to-from);
	sys_path.erase(std::remove_if(sys_path.begin(), sys_path.end(), isspace), sys_path.end());
	if (!dynpath.EndsWith(":")) dynpath += ":";
	dynpath += sys_path.c_str();
	}
	dynpath.ReplaceAll("::", ":");
	#endif

[guitargeek]

I think that's unrelated and maybe still needed to fix https://its.cern.ch/jira/browse/ROOT-5858. See also the commit that reproduces it:

• 0a0b2dd

Why you're asking? Is there another GitHub issue or Jira ticket related to it?

[github-actions]

Test Results

    21 files      21 suites   3d 22h 20m 55s ⏱️
 3 667 tests  3 662 ✅ 0 💤 5 ❌
75 189 runs  75 175 ✅ 5 💤 9 ❌

For more details on these failures, see this check.

Results for commit d345257.

[ferdymercury]

Why you're asking?

Just because it was mentioned in the description of https://its.cern.ch/jira/browse/ROOT-9758

[pcanal]

The reason to set CMAKE_SKIP_INSTALL_RPATH is usually because ROOT is intended to be installed into directories that are already in the paths,

Can you produce a relocatable build without CMAKE_SKIP_INSTALL_RPATH ?

because ROOT is intended to be installed into directories that are already in the paths

Yes maybe ... but one of the 'point' of the root executable is to be (as opposed to root.exe) self sufficient (i.e. no need to set LD_LIBRARY_PATH nor ROOTSYS) even if the build was relocated.