target_link_libraries: Place $<TARGET_OBJECTS> before libraries

Linkers always use object files explicitly specified on the command line
regardless of where they appear.  Move them to the front of the list of
linked libraries in so that symbols required by the object files can be
resolved by any library.

Issue: #22149

14 files changed, 151 insertions, 0 deletions

diff --git a/Tests/ObjectLibrary/CMakeLists.txt b/Tests/ObjectLibrary/CMakeLists.txt
index 74f34e4..06167a8 100644
--- a/Tests/ObjectLibrary/CMakeLists.txt
+++ b/Tests/ObjectLibrary/CMakeLists.txt
@@ -74,4 +74,6 @@ target_link_libraries(UseABstaticObjs ABstatic)
 
 add_subdirectory(ExportLanguages)
 
+add_subdirectory(LinkObjects)
+
 add_subdirectory(Transitive)
diff --git a/Tests/ObjectLibrary/LinkObjects/CMakeLists.txt b/Tests/ObjectLibrary/LinkObjects/CMakeLists.txt
new file mode 100644
index 0000000..899be45
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/CMakeLists.txt
@@ -0,0 +1,45 @@
+add_executable(LinkObjects main.c)
+
+# Link TARGET_OBJECTS through LINK_LIBRARIES.
+add_library(LinkObjectsAObj OBJECT a_obj.c)
+add_library(LinkObjectsADep STATIC a_dep.c)
+target_compile_definitions(LinkObjectsAObj PUBLIC OBJA)
+target_link_libraries(LinkObjects PRIVATE LinkObjectsADep $<TARGET_OBJECTS:LinkObjectsAObj>)
+
+# Link TARGET_OBJECTS through INTERFACE_LINK_LIBRARIES with usage requirements.
+add_library(LinkObjectsB INTERFACE)
+add_library(LinkObjectsBObj OBJECT b_obj.c)
+add_library(LinkObjectsBDep STATIC b_dep.c)
+target_compile_definitions(LinkObjectsBObj PUBLIC OBJB)
+target_link_libraries(LinkObjectsB INTERFACE LinkObjectsBObj $<TARGET_OBJECTS:LinkObjectsBObj>)
+target_link_libraries(LinkObjectsBObj PRIVATE LinkObjectsBDep)
+target_link_libraries(LinkObjects PRIVATE LinkObjectsB)
+
+# Link TARGET_OBJECTS through INTERFACE_LINK_LIBRARIES without usage requirements.
+add_library(LinkObjectsC INTERFACE)
+add_library(LinkObjectsCObj OBJECT c_obj.c)
+add_library(LinkObjectsCDep STATIC c_dep.c)
+target_compile_definitions(LinkObjectsCObj PUBLIC OBJC)
+target_link_libraries(LinkObjectsC INTERFACE LinkObjectsCDep $<TARGET_OBJECTS:LinkObjectsCObj>)
+target_link_libraries(LinkObjectsCObj PRIVATE LinkObjectsCDep)
+target_link_libraries(LinkObjects PRIVATE LinkObjectsC)
+
+# Link TARGET_OBJECTS through both LINK_LIBRARIES and INTERFACE_LINK_LIBRARIES, deduplicated.
+add_library(LinkObjectsD INTERFACE)
+add_library(LinkObjectsDObj OBJECT d_obj.c)
+add_library(LinkObjectsDDep STATIC d_dep.c)
+target_compile_definitions(LinkObjectsDObj PUBLIC OBJD)
+target_link_libraries(LinkObjectsD INTERFACE LinkObjectsDObj $<TARGET_OBJECTS:LinkObjectsDObj>)
+target_link_libraries(LinkObjectsDObj PRIVATE LinkObjectsDDep)
+target_link_libraries(LinkObjects PRIVATE $<TARGET_OBJECTS:LinkObjectsDObj> LinkObjectsD)
+
+# Link TARGET_OBJECTS through STATIC library private dependency.
+add_library(LinkObjectsE INTERFACE)
+add_library(LinkObjectsEObj OBJECT e_obj.c)
+add_library(LinkObjectsEDep STATIC e_dep.c)
+add_library(LinkObjectsEStatic STATIC e_lib.c)
+target_compile_definitions(LinkObjectsEObj PUBLIC OBJE)
+target_link_libraries(LinkObjectsE INTERFACE LinkObjectsEObj $<TARGET_OBJECTS:LinkObjectsEObj>)
+target_link_libraries(LinkObjectsEObj PRIVATE LinkObjectsEDep)
+target_link_libraries(LinkObjectsEStatic PRIVATE LinkObjectsE)
+target_link_libraries(LinkObjects PRIVATE LinkObjectsEStatic)
diff --git a/Tests/ObjectLibrary/LinkObjects/a_dep.c b/Tests/ObjectLibrary/LinkObjects/a_dep.c
new file mode 100644
index 0000000..0128740
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/a_dep.c
@@ -0,0 +1,7 @@
+#ifdef OBJA
+#  error "OBJA is defined, but should not be"
+#endif
+int a_dep(void)
+{
+  return 0;
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/a_obj.c b/Tests/ObjectLibrary/LinkObjects/a_obj.c
new file mode 100644
index 0000000..5e79c60
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/a_obj.c
@@ -0,0 +1,8 @@
+#ifndef OBJA
+#  error "OBJA is not defined, but should be"
+#endif
+extern int a_dep(void);
+int a_obj(void)
+{
+  return a_dep();
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/b_dep.c b/Tests/ObjectLibrary/LinkObjects/b_dep.c
new file mode 100644
index 0000000..ad5d367
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/b_dep.c
@@ -0,0 +1,7 @@
+#ifdef OBJB
+#  error "OBJB is defined, but should not be"
+#endif
+int b_dep(void)
+{
+  return 0;
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/b_obj.c b/Tests/ObjectLibrary/LinkObjects/b_obj.c
new file mode 100644
index 0000000..d0f426a
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/b_obj.c
@@ -0,0 +1,8 @@
+#ifndef OBJB
+#  error "OBJB is not defined, but should be"
+#endif
+extern int b_dep(void);
+int b_obj(void)
+{
+  return b_dep();
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/c_dep.c b/Tests/ObjectLibrary/LinkObjects/c_dep.c
new file mode 100644
index 0000000..1d99ab8
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/c_dep.c
@@ -0,0 +1,7 @@
+#ifdef OBJC
+#  error "OBJC is defined, but should not be"
+#endif
+int c_dep(void)
+{
+  return 0;
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/c_obj.c b/Tests/ObjectLibrary/LinkObjects/c_obj.c
new file mode 100644
index 0000000..08fa5f5
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/c_obj.c
@@ -0,0 +1,8 @@
+#ifndef OBJC
+#  error "OBJC is not defined, but should be"
+#endif
+extern int c_dep(void);
+int c_obj(void)
+{
+  return c_dep();
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/d_dep.c b/Tests/ObjectLibrary/LinkObjects/d_dep.c
new file mode 100644
index 0000000..cf09314
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/d_dep.c
@@ -0,0 +1,7 @@
+#ifdef OBJD
+#  error "OBJD is defined, but should not be"
+#endif
+int d_dep(void)
+{
+  return 0;
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/d_obj.c b/Tests/ObjectLibrary/LinkObjects/d_obj.c
new file mode 100644
index 0000000..d14ce66
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/d_obj.c
@@ -0,0 +1,8 @@
+#ifndef OBJD
+#  error "OBJD is not defined, but should be"
+#endif
+extern int d_dep(void);
+int d_obj(void)
+{
+  return d_dep();
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/e_dep.c b/Tests/ObjectLibrary/LinkObjects/e_dep.c
new file mode 100644
index 0000000..7fb70c1
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/e_dep.c
@@ -0,0 +1,7 @@
+#ifdef OBJE
+#  error "OBJE is defined, but should not be"
+#endif
+int e_dep(void)
+{
+  return 0;
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/e_lib.c b/Tests/ObjectLibrary/LinkObjects/e_lib.c
new file mode 100644
index 0000000..9bb3a44
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/e_lib.c
@@ -0,0 +1,5 @@
+extern int e_obj(void);
+int e_lib(void)
+{
+  return e_obj();
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/e_obj.c b/Tests/ObjectLibrary/LinkObjects/e_obj.c
new file mode 100644
index 0000000..02624eb
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/e_obj.c
@@ -0,0 +1,8 @@
+#ifndef OBJE
+#  error "OBJE is not defined, but should be"
+#endif
+extern int e_dep(void);
+int e_obj(void)
+{
+  return e_dep();
+}
diff --git a/Tests/ObjectLibrary/LinkObjects/main.c b/Tests/ObjectLibrary/LinkObjects/main.c
new file mode 100644
index 0000000..c09c4f1
--- /dev/null
+++ b/Tests/ObjectLibrary/LinkObjects/main.c
@@ -0,0 +1,24 @@
+#ifdef OBJA
+#  error "OBJA is defined, but should not be"
+#endif
+#ifndef OBJB
+#  error "OBJB is not defined, but should be"
+#endif
+#ifdef OBJC
+#  error "OBJC is defined, but should not be"
+#endif
+#ifndef OBJD
+#  error "OBJD is not defined, but should be"
+#endif
+#ifdef OBJE
+#  error "OBJE is defined, but should not be"
+#endif
+extern int a_obj(void);
+extern int b_obj(void);
+extern int c_obj(void);
+extern int d_obj(void);
+extern int e_lib(void);
+int main(void)
+{
+  return a_obj() + b_obj() + c_obj() + d_obj() + e_lib();
+}