[contrib] Disable GCC warnings and broken features (#37131)

Currently contrib does not build with GCC because of various false
positive compiler warnings turned to errors and a GCC compiler bug.

Let's first start with the bug, in GCC apparently
using -gsplit-dwarf (debug fission) and -fdebug-types-section (used to
optimize the size of debug inforamtion), when used together, can result
in a linker failure.

Refer to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885 for the GCC
bug report of this issue. When it comes to Envoy, optimized builds with
GCC are affected on at least GCC 11 (used by --config=docker-gcc) and
GCC 12 (and I'm pretty sure the bug isn't fixed in any newer versions
either, though I didn't check each version).

Given that we cannot have both debug fission and a debug types section,
we decided to abandon the debug types sections and keep the fission.

That being said, apparently both of those options are unmaintained in
GCC which poses a question of long term viability of using those or GCC.

Other changes in this commit disable GCC compiler errors for various
warnings that happen when building contrib. I checked those warnings and
didn't find any true
positive.

And additionally, for warnings that exists in both Clang and GCC, Clang
warnings don't trigger, so Clang also disagrees with GCC here.

Additionally missing-requires warning is new and does not exist in GCC
11, but exists in later versions of GCC, so to avoid breaking on this
warning for future versions of GCC I disabled it, but also tell GCC to
not complain if it sees a flag related to an unknwon diagnostic.

This is the last change required to make GCC contrib builds work (you
can find more context and discussions in
#31807)

Risk Level: Low
Testing: building with --config=gcc and --config=docker-gcc
Docs Changes: N/A
Release Notes: N/A
Platform Specific Features: N/A
Fixes #31807

Signed-off-by: Mikhail Krinkin <[email protected]>

.bazelrc

@@ -57,9 +57,9 @@ test --experimental_ui_max_stdouterr_bytes=11712829 #default 1048576
 # Allow tags to influence execution requirements
 common --experimental_allow_tags_propagation
 
+build:linux --copt=-fdebug-types-section
 # Enable position independent code (this is the default on macOS and Windows)
 # (Workaround for https://github.com/bazelbuild/rules_foreign_cc/issues/421)
-build:linux --copt=-fdebug-types-section
 build:linux --copt=-fPIC
 build:linux --copt=-Wno-deprecated-declarations
 build:linux --cxxopt=-std=c++20 --host_cxxopt=-std=c++20
@@ -95,6 +95,21 @@ build:gcc --linkopt=-fuse-ld=gold --host_linkopt=-fuse-ld=gold
 build:gcc --test_env=HEAPCHECK=
 build:gcc --action_env=BAZEL_COMPILER=gcc
 build:gcc --action_env=CC=gcc --action_env=CXX=g++
+# This is to work around a bug in GCC that makes debug-types-section
+# option not play well with fission:
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885
+build:gcc --copt=-fno-debug-types-section
+# These trigger errors in multiple places both in Envoy dependecies
+# and in Envoy code itself when using GCC.
+# And in all cases the reports appear to be clear false positives.
+build:gcc --copt=-Wno-error=restrict
+build:gcc --copt=-Wno-error=uninitialized
+build:gcc --cxxopt=-Wno-missing-requires
+# We need this because -Wno-missing-requires options is rather new
+# in GCC, so flags -Wno-missing-requires exists in GCC 12, but does
+# not in GCC 11 and GCC 11 is what is used in docker-gcc
+# configuration currently
+build:gcc --cxxopt=-Wno-unknown-warning
 
 # Clang-tidy
 # TODO(phlax): enable this, its throwing some errors as well as finding more issues
@@ -375,6 +390,7 @@ build:docker-clang-libc++ --config=docker-sandbox
 build:docker-clang-libc++ --config=rbe-toolchain-clang-libc++
 
 build:docker-gcc --config=docker-sandbox
+build:docker-gcc --config=gcc
 build:docker-gcc --config=rbe-toolchain-gcc
 
 build:docker-asan --config=docker-sandbox

bazel/envoy_internal.bzl

@@ -68,7 +68,21 @@ def envoy_copts(repository, test = False):
                    "-Wc++2a-extensions",
                    "-Wrange-loop-analysis",
                ],
-               repository + "//bazel:gcc_build": ["-Wno-maybe-uninitialized"],
+               repository + "//bazel:gcc_build": [
+                   "-Wno-maybe-uninitialized",
+                   # GCC implementation of this warning is too noisy.
+                   #
+                   # It generates warnings even in cases where there is no ambiguity
+                   # between the overloaded version of a method and the hidden version
+                   # from the base class. E.g., when the two have different number of
+                   # arguments or incompatible types and therefore a wrong function
+                   # cannot be called by mistake without triggering a compiler error.
+                   #
+                   # As a safeguard, this warning is only disabled for GCC builds, so
+                   # if Clang catches a problem in the code we would get a warning
+                   # anyways.
+                   "-Wno-error=overloaded-virtual",
+               ],
                # Allow 'nodiscard' function results values to be discarded for test code only
                # TODO(envoyproxy/windows-dev): Replace /Zc:preprocessor with /experimental:preprocessor
                # for msvc versions between 15.8 through 16.4.x. see