build_scripts/Linux: Try to determine library dependencies with ldd first

The build scripts used a reimplementation of ldd to determine
library dependencies in case ldd is not installed which may
fail on recent systems.
Try ldd first and fall back to the reimplementation only
if it fails.

Change-Id: Icca16c2fae0ce6086284eb0194a28d8ec32daae6
Reviewed-by: Simo Fält <simo.falt@qt.io>

1 files changed, 60 insertions, 4 deletions

diff --git a/build_scripts/utils.py b/build_scripts/utils.py
index 0a9036905..abe0b2c05 100644
--- a/build_scripts/utils.py
+++ b/build_scripts/utils.py
@@ -802,18 +802,48 @@ def ldd_get_paths_for_dependencies(dependencies_regex, executable_path=None, dep
     return paths
 
 
-def ldd(executable_path):
+def _ldd_ldd(executable_path):
+    """Helper for ldd():
+       Returns ldd output of shared library dependencies for given
+       `executable_path`.
+
+    Parameters
+    ----------
+    executable_path : str
+        path to executable or shared library.
+
+    Returns
+    -------
+    output : str
+        the raw output retrieved from the dynamic linker.
+    """
+
+    output = ''
+    error = ''
+    try:
+        output_lines = run_process_output(['ldd', executable_path])
+        output = '\n'.join(output_lines)
+    except Exception as e:
+        error = str(e)
+    if not output:
+        message = f"ldd failed to query for dependent shared libraries of {executable_path}: {error}"
+        raise RuntimeError(message)
+    return output
+
+
+def _ldd_ldso(executable_path):
     """
+    Helper for ldd():
     Returns ld.so output of shared library dependencies for given
     `executable_path`.
 
-    This is a partial port of /usr/bin/ldd from bash to Python.
+    This is a partial port of /usr/bin/ldd from bash to Python for
+    systems that do not have ldd.
     The dependency list is retrieved by setting the
     LD_TRACE_LOADED_OBJECTS=1 environment variable, and executing the
     given path via the dynamic loader ld.so.
 
-    Only works on Linux. The port is required to make this work on
-    systems that might not have ldd.
+    Only works on Linux.
     This is because ldd (on Ubuntu) is shipped in the libc-bin package
     that, which might have a
     minuscule percentage of not being installed.
@@ -862,6 +892,32 @@ def ldd(executable_path):
                            f"libraries of {executable_path}")
 
 
+def ldd(executable_path):
+    """
+    Returns ldd output of shared library dependencies for given `executable_path`,
+    using either ldd or ld.so depending on availability.
+
+    Parameters
+    ----------
+    executable_path : str
+        path to executable or shared library.
+
+    Returns
+    -------
+    output : str
+        the raw output retrieved from the dynamic linker.
+    """
+    result = ''
+    try:
+        result = _ldd_ldd(executable_path)
+    except RuntimeError as e:
+        message = f"ldd: Falling back to ld.so ({str(e)})"
+        log.warn(message)
+    if not result:
+        result = _ldd_ldso(executable_path)
+    return result
+
+
 def find_files_using_glob(path, pattern):
     """ Returns list of files that matched glob `pattern` in `path`. """
     final_pattern = os.path.join(path, pattern)