[llvm] [bazel] Rework liblldb (PR #91549)

[Aaron Siddhartha Mondal via llvm-commits]

================
@@ -728,37 +728,57 @@ cc_library(
     ],
 )
 
-cc_library(
-    name = "liblldb.static",
-    deps = [
-        ":API",
-        ":Interpreter",
-    ],
+genrule(
+    name = "gen_exports_file_linux",
+    srcs = ["//lldb:source/API/liblldb-private.exports"],
+    outs = ["exports_linux.txt"],
+    cmd = """
+cat > $(OUTS) <<EOF
+{
+  global:
+    $$(sed 's/$$/;/g' $(SRCS))
+};
+EOF
+""",
 )
 
-cc_shared_library(
-    name = "liblldb",
-    # TODO: Remove once fixed https://github.com/bazelbuild/bazel/issues/21893
+genrule(
+    name = "gen_exports_file_macos",
+    srcs = ["//lldb:source/API/liblldb-private.exports"],
+    outs = ["exports_macos.txt"],
+    cmd = "sed 's/^/_/g' $(SRCS) > $(OUTS)",
+)
+
+cc_binary(
+    name = "lldb{}".format(PACKAGE_VERSION),
     additional_linker_inputs = select({
+        "@platforms//os:linux": [
+            ":gen_exports_file_linux",
+        ],
         "@platforms//os:macos": [
-            ":HostMacOSXObjCXX",
-            "//lldb/source/Plugins:PluginPlatformMacOSXObjCXX",
+            ":gen_exports_file_macos",
         ],
         "//conditions:default": [],
     }),
-    shared_lib_name = select({
-        "@platforms//os:macos": "liblldb{}.dylib".format(PACKAGE_VERSION),
-        "@platforms//os:linux": "liblldb{}.so".format(PACKAGE_VERSION),
-    }),
-    # TODO: Remove once fixed https://github.com/bazelbuild/bazel/issues/21893
-    user_link_flags = select({
+    linkopts = select({
+        "@platforms//os:linux": [
+            "-Wl,--export-dynamic-symbol-list=$(location :gen_exports_file_linux)",
+        ],
         "@platforms//os:macos": [
-            "$(location :HostMacOSXObjCXX)",
-            "$(location //lldb/source/Plugins:PluginPlatformMacOSXObjCXX)",
+            "-Wl,-exported_symbols_list,$(location :gen_exports_file_macos)",
         ],
         "//conditions:default": [],
     }),
-    deps = [":liblldb.static"],
+    linkshared = True,
----------------
aaronmondal wrote:

Oh wow I was quite confused that we can't use a `cc_library` with `linkshared = True`, but apparently that wouldn't link the deps into the shared object lol https://bazel.build/reference/be/c-cpp#cc_library.linkopts

Meahwhile I'm having good times with just an `emit` attribute :stuck_out_tongue: https://ll.eomii.org/rules/defs/#ll_library-emit

https://github.com/llvm/llvm-project/pull/91549