turn on -Wall with a few exceptions in Bazel build

Summary:
We add the following exceptions:
 * sign-compare: this is heavily violated in our codebase
 * unknown-pragmas: we use this intentionally for some loop unrolling
   in CUDA

Because they are included in -Wall by default, we remove the following
warnings from our explicit list:
 * unused-function
 * unused-variable

Test Plan: Rely on CI.

Reviewers: alband, seemethere

Subscribers:

Tasks:

Tags:

Pull Request resolved: pytorch#79306

Approved by: https://github.com/malfet

.bazelrc

@@ -58,8 +58,17 @@ build:cpu-only --@rules_cuda//cuda:enable_cuda=False
 #    macro-level opts will come earlier than target level overrides
 build --per_file_copt='^//.*\.(cpp|cc)$'@-Werror=type-limits
 build --per_file_copt='^//.*\.(cpp|cc)$'@-Werror=unused-but-set-variable
-build --per_file_copt='^//.*\.(cpp|cc)$'@-Werror=unused-function
-build --per_file_copt='^//.*\.(cpp|cc)$'@-Werror=unused-variable
+
+build --per_file_copt='^//.*\.(cpp|cc)$'@-Werror=all
+# The following warnings come from -Wall. We downgrade them from error
+# to warnings here.
+#
+# sign-compare has a tremendous amount of violations in the
+# codebase. It will be a lot of work to fix them, just disable it for
+# now.
+build --per_file_copt='^//.*\.(cpp|cc)$'@-Wno-sign-compare
+# We intentionally use #pragma unroll, which is compiler specific.
+build --per_file_copt='^//.*\.(cpp|cc)$'@-Wno-error=unknown-pragmas
 
 build --per_file_copt='//:aten/src/ATen/RegisterCompositeExplicitAutograd\.cpp$'@-Wno-error=unused-function
 build --per_file_copt='//:aten/src/ATen/RegisterCompositeImplicitAutograd\.cpp$'@-Wno-error=unused-function

tools/rules/cu.bzl

@@ -5,8 +5,17 @@ NVCC_COPTS = [
     "--expt-extended-lambda",
     "--compiler-options=-Werror=type-limits",
     "--compiler-options=-Werror=unused-but-set-variable",
-    "--compiler-options=-Werror=unused-function",
-    "--compiler-options=-Werror=unused-variable",
+
+    "--compiler-options=-Werror=all",
+    # The following warnings come from -Wall. We downgrade them from
+    # error to warnings here.
+    #
+    # sign-compare has a tremendous amount of violations in the
+    # codebase. It will be a lot of work to fix them, just disable it
+    # for now.
+    "--compiler-options=-Wno-sign-compare",
+    # We intentionally use #pragma unroll, which is compiler specific.
+    "--compiler-options=-Wno-error=unknown-pragmas",
 ]
 
 def cu_library(name, srcs, copts = [], **kwargs):