cmake: Only propagate interface link flags in dep

CMake has two target properties, LINK_OPTIONS and INTERFACE_LINK_OPTIONS.
The former is for link flags that apply only to the target (PRIVATE).
The latter is used for link flags that propagate to dependents (PUBLIC
or INTERFACE). Meson currently propagates all flags, PUBLIC and PRIVATE,
as part of the generated dependency() which causes problems when some of
the private flags are highly disruptive, e.g. `-Wl,--version-script`.

Tease apart the two kinds of link flags and, for non-static libraries,
only propagate the PUBLIC/INTERFACE flags and not the PRIVATE ones.

3 files changed, 20 insertions, 2 deletions

diff --git a/docs/markdown/snippets/cmake_only_public_link_flags_in_dep.md b/docs/markdown/snippets/cmake_only_public_link_flags_in_dep.md
new file mode 100644
index 000000000..83ccfd439
--- /dev/null
+++ b/docs/markdown/snippets/cmake_only_public_link_flags_in_dep.md
@@ -0,0 +1,8 @@
+## Dependencies from CMake subprojects now use only PUBLIC link flags
+
+Any [[@dep]] obtained from a CMake subproject (or `.wrap` with `method = cmake`)
+now only includes link flags marked in CMake as `PUBLIC` or `INTERFACE`.
+Flags marked as `PRIVATE` are now only applied when building the subproject
+library and not when using it as a dependency. This better matches how CMake
+handles link flags and fixes link errors when using some CMake projects as
+subprojects.
diff --git a/mesonbuild/cmake/interpreter.py b/mesonbuild/cmake/interpreter.py
index 5e6cde653..1f82f875b 100644
--- a/mesonbuild/cmake/interpreter.py
+++ b/mesonbuild/cmake/interpreter.py
@@ -223,6 +223,7 @@ class ConverterTarget:
         self.install_dir: T.Optional[Path] = None
         self.link_libraries = target.link_libraries
         self.link_flags = target.link_flags + target.link_lang_flags
+        self.public_link_flags: T.List[str] = []
         self.depends_raw: T.List[str] = []
         self.depends: T.List[T.Union[ConverterTarget, ConverterCustomTarget]] = []
 
@@ -347,6 +348,7 @@ class ConverterTarget:
             rtgt = resolve_cmake_trace_targets(self.cmake_name, trace, self.env)
             self.includes += [Path(x) for x in rtgt.include_directories]
             self.link_flags += rtgt.link_flags
+            self.public_link_flags += rtgt.public_link_flags
             self.public_compile_opts += rtgt.public_compile_opts
             self.link_libraries += rtgt.libraries
 
@@ -1167,12 +1169,18 @@ class CMakeInterpreter:
 
             # declare_dependency kwargs
             dep_kwargs: TYPE_mixed_kwargs = {
-                'link_args': tgt.link_flags + tgt.link_libraries,
                 'link_with': id_node(tgt_var),
                 'compile_args': tgt.public_compile_opts,
                 'include_directories': id_node(inc_var),
             }
 
+            # Static libraries need all link options and transient dependencies, but other
+            # libraries should only use the link flags from INTERFACE_LINK_OPTIONS.
+            if tgt_func == 'static_library':
+                dep_kwargs['link_args'] = tgt.link_flags + tgt.link_libraries
+            else:
+                dep_kwargs['link_args'] = tgt.public_link_flags
+
             if dependencies:
                 generated += dependencies
 
diff --git a/mesonbuild/cmake/tracetargets.py b/mesonbuild/cmake/tracetargets.py
index 5a9d35284..2cc0c1722 100644
--- a/mesonbuild/cmake/tracetargets.py
+++ b/mesonbuild/cmake/tracetargets.py
@@ -42,6 +42,7 @@ class ResolvedTarget:
     def __init__(self) -> None:
         self.include_directories: T.List[str] = []
         self.link_flags:          T.List[str] = []
+        self.public_link_flags:   T.List[str] = []
         self.public_compile_opts: T.List[str] = []
         self.libraries:           T.List[str] = []
 
@@ -111,7 +112,8 @@ def resolve_cmake_trace_targets(target_name: str,
             res.include_directories += [x for x in tgt.properties['INTERFACE_INCLUDE_DIRECTORIES'] if x]
 
         if 'INTERFACE_LINK_OPTIONS' in tgt.properties:
-            res.link_flags += [x for x in tgt.properties['INTERFACE_LINK_OPTIONS'] if x]
+            res.public_link_flags += [x for x in tgt.properties['INTERFACE_LINK_OPTIONS'] if x]
+            res.link_flags += res.public_link_flags
 
         if 'INTERFACE_COMPILE_DEFINITIONS' in tgt.properties:
             res.public_compile_opts += ['-D' + re.sub('^-D', '', x) for x in tgt.properties['INTERFACE_COMPILE_DEFINITIONS'] if x]