Makefile improvements

- Add an "all" build target
- Fix build if libcuda.so is not on linker search path
- Do not assume that nvcc is available on $PATH
- Allow specifying CFLAGS and LDFLAGS when running make
- Allow passing non-standard CUDA build locations to make

Suggested usage if CUDA is installed in a non-standard location,
say, /playpen/jbakita/CUDA/cuda-archive/cuda-12.2:

make CUDA=/playpen/jbakita/CUDA/cuda-archive/cuda-12.2

2 files changed, 20 insertions, 12 deletions

diff --git a/Makefile b/Makefile
index 5af440e..5256634 100644
--- a/Makefile
+++ b/Makefile
@@ -1,22 +1,28 @@
+# Set this if CUDA is installed in a different location
+CUDA ?= /usr/local/cuda
 # Note that CXX and CC are predefined as g++ and cc (respectively) by Make
-NVCC ?= nvcc
-# -fPIC is needed in all cases, as we may be linked into another shared library
-CFLAGS = -fPIC
-LDFLAGS = -lcuda -I/usr/local/cuda/include
+NVCC ?= $(CUDA)/bin/nvcc
+# Everything has to have -lcuda, as it's needed for libsmctrl
+LDFLAGS := -lcuda -I$(CUDA)/include -L$(CUDA)/lib64
 
-.PHONY: clean tests
+.PHONY: clean tests all
 
+# ----- Main Library -----
 libsmctrl.so: libsmctrl.c libsmctrl.h
-        $(CC) $< -shared -o $@ $(CFLAGS) $(LDFLAGS)
+        $(CC) $< -shared -o $@ -fPIC $(CFLAGS) $(LDFLAGS)
 
+# -fPIC is needed even if built as a static library, in case we are linked into
+# another shared library
 libsmctrl.a: libsmctrl.c libsmctrl.h
-        $(CC) $< -c -o libsmctrl.o $(CFLAGS) $(LDFLAGS)
+        $(CC) $< -c -o libsmctrl.o -fPIC $(CFLAGS) $(LDFLAGS)
         ar rcs $@ libsmctrl.o
 
+# ----- Utilities -----
 # Use static linking with tests to avoid LD_LIBRARY_PATH issues
 libsmctrl_test_gpc_info: libsmctrl_test_gpc_info.c libsmctrl.a testbench.h
-        $(CC) $< -o $@ -g -L. -l:libsmctrl.a $(LDFLAGS)
+        $(CC) $< -o $@ -g -L. -l:libsmctrl.a $(CFLAGS) $(LDFLAGS)
 
+# ----- Tests -----
 libsmctrl_test_mask_shared.o: libsmctrl_test_mask_shared.cu testbench.h
         $(NVCC) -ccbin $(CXX) $< -c -g
 
@@ -37,6 +43,8 @@ libsmctrl_test_next_mask_override: libsmctrl_test_next_mask_override.c libsmctrl
 
 tests: libsmctrl_test_gpc_info libsmctrl_test_global_mask libsmctrl_test_stream_mask libsmctrl_test_stream_mask_override libsmctrl_test_next_mask libsmctrl_test_next_mask_override
 
+all: libsmctrl.so tests
+
 clean:
         rm -f libsmctrl.so libsmctrl.a libsmctrl_test_gpu_info \
               libsmctrl_test_mask_shared.o libmsctrl_test_global_mask \
diff --git a/README.md b/README.md
index c3f87c4..f4d7cd1 100644
--- a/README.md
+++ b/README.md
@@ -29,10 +29,10 @@ To build, ensure that you have `gcc` installed and access to the CUDA SDK includ
 make libsmctrl.a
 ```
 
-If you see an error that the command `nvcc` was not found, `nvcc` is not available on your `PATH`.
-Correct this error by explictly specifying the location of `nvcc` to `make`, e.g.:
+If you see errors about CUDA headers or libraries not being found, your CUDA installation may be in a non-standard location.
+Correct this error by explictly specifying the location of the CUDA install `make`, e.g.:
 ```
-make NVCC=/playpen/jbakita/CUDA/cuda-archive/cuda-10.2/bin/nvcc libsmctrl.a
+make CUDA=/playpen/jbakita/CUDA/cuda-archive/cuda-10.2/ libsmctrl.a
 ```
 
 For binary backwards-compatibility to old versions of the NVIDIA GPU driver, we recommend building with an old version of the CUDA SDK.
@@ -41,7 +41,7 @@ For example, by building against CUDA 10.2, the binary will be compatible with a
 Older versions of `nvcc` may require you to use an older version of `g++`.
 This can be explictly specified via the `CXX` variable, e.g.:
 ```
-make NVCC=/playpen/jbakita/CUDA/cuda-archive/cuda-8.0/bin/nvcc CXX=g++-5 libsmctrl.a
+make CUDA=/playpen/jbakita/CUDA/cuda-archive/cuda-8.0/ CXX=g++-5 libsmctrl.a
 ```
 
 `libsmctrl` supports being built as a shared library.