igvm_c: Fix linker issues with sample and tests and clean up output (#31

)

It was reported on coconut-svsm/svsm#237 that on
certain environments, the C unit tests and sample fail to build due to
missing library dependencies. Also, the status of the build is hard to
determine due to the amount of warnings generated by cbindgen. See the
comment thread in that PR from @cclaudio.

The required list of libraries can be determined with the following
command:

```
cargo rustc --verbose --features "igvm-c" --manifest-path=igvm/Cargo.toml -- --print=native-static-libs
```
This PR updates the Makefile to reflect the output of this command. In
addition, the cbindgen `-q` flag is used to suppress warnings - it would
be good to fix the warnings but this would require the generation of
redundant additional output in the header files which is not ideal.

Finally, add a section to the README to describe how to install the
library.

---------

Signed-off-by: Roy Hopkins <[email protected]>
Co-authored-by: Chris Oo <[email protected]>

igvm_c/Makefile

@@ -35,14 +35,14 @@ $(TARGET_PATH)/test_data:
 	$(CARGO) build --manifest-path=$(IGVM_DIR)/igvm_c/test_data/Cargo.toml
 
 include/igvm.h: $(RUST_SOURCE)
-	cbindgen -c $(API_DIR)/cbindgen_igvm.toml $(IGVM_DIR)/igvm -o "$(API_DIR)/include/igvm.h"
-	cbindgen -c $(API_DIR)/cbindgen_igvm_defs.toml $(IGVM_DIR)/igvm_defs -o "$(API_DIR)/include/igvm_defs.h"
+	cbindgen -q -c $(API_DIR)/cbindgen_igvm.toml $(IGVM_DIR)/igvm -o "$(API_DIR)/include/igvm.h"
+	cbindgen -q -c $(API_DIR)/cbindgen_igvm_defs.toml $(IGVM_DIR)/igvm_defs -o "$(API_DIR)/include/igvm_defs.h"
 
 $(TARGET_PATH)/dump_igvm: $(API_DIR)/include/igvm.h $(API_DIR)/sample/dump_igvm.c $(TARGET_PATH)/libigvm.a
-	cc -g3 -O0 -I $(API_DIR) -L $(TARGET_PATH) -o $@ $^ -ligvm -lcunit
+	cc -g3 -O0 -I $(API_DIR) -L $(TARGET_PATH) -o $@ $^ -ligvm -ldl -pthread -lm -lutil -lrt
 
 $(TARGET_PATH)/igvm_test: $(API_DIR)/include/igvm.h $(API_DIR)/tests/igvm_test.c $(TARGET_PATH)/libigvm.a
-	cc -g3 -O0 -I $(API_DIR) -L $(TARGET_PATH) -o $@ $^ -ligvm -lcunit
+	cc -g3 -O0 -I $(API_DIR) -L $(TARGET_PATH) -o $@ $^ -ligvm -lcunit -ldl -pthread -lm -lutil -lrt
 
 $(TARGET_PATH)/igvm.bin: $(TARGET_PATH)/test_data
 	$(TARGET_PATH)/test_data $(TARGET_PATH)/igvm.bin

igvm_c/README.md

@@ -45,6 +45,21 @@ exported C functions.
 The file `igvm.h` includes `igvm_defs.h` so only this file needs to be included
 in C projects source files.
 
+## Installing
+Once built, the library can be installed with:
+
+```bash
+make -f Makefile install
+```
+
+By default, the library will be installed into `/usr` which will require root
+privileges. Alternatively, the library can be installed in a different location
+by setting `PREFIX`:
+
+```bash
+PREFIX=/path/to/installation make -f Makefile install
+```
+
 ## Sample application
 The C API build generates a test application named `dump_igvm`. This application
 can take the path of a binary IGVM file as a parameter and will use the C API to