[cff] Some CFF files fail to build with warnings in Chrome

[drott]

Compare Chromium build output from:

https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8928054094769963200/+/steps/compile__with_patch_/0/stdout

via the experimental HB roll CL in:
https://chromium-review.googlesource.com/c/chromium/src/+/1361067

FAILED: obj/third_party/harfbuzz-ng/harfbuzz_source/hb-ot-cff1-table.o 
/b/swarming/w/ir/cache/goma/client/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/third_party/harfbuzz-ng/harfbuzz_source/hb-ot-cff1-table.o.d -DHAVE_OT -DHAVE_ICU -DHAVE_ICU_BUILTIN -DHAVE_INTEL_ATOMIC_PRIMITIVES -DHB_NO_MMAP -DV8_DEPRECATION_WARNINGS -DDCHECK_ALWAYS_ON=1 -DUSE_UDEV -DUSE_AURA=1 -DUSE_GLIB=1 -DUSE_NSS_CERTS=1 -DUSE_X11=1 -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DCHROMIUM_BUILD -DFIELDTRIAL_TESTING_ENABLED -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_GNU_SOURCE -DCR_CLANG_REVISION=\"346388-5\" -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS -DCR_LIBCXX_REVISION=344254 -DCR_LIBCXXABI_REVISION=344215 -D_LIBCPP_ENABLE_NODISCARD -DCR_SYSROOT_HASH=e7c53f04bd88d29d075bfd1f62b073aeb69cbe09 -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DFT_CONFIG_CONFIG_H=\"freetype-custom-config/ftconfig.h\" -DFT_CONFIG_MODULES_H=\"freetype-custom-config/ftmodule.h\" -DFT_CONFIG_OPTIONS_H=\"freetype-custom-config/ftoption.h\" -DPDFIUM_REQUIRED_MODULES -DCHROMIUM_RESTRICT_VISIBILITY -DGLIB_VERSION_MAX_ALLOWED=GLIB_VERSION_2_32 -DGLIB_VERSION_MIN_REQUIRED=GLIB_VERSION_2_26 -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DUSE_CHROMIUM_ICU=1 -DU_STATIC_IMPLEMENTATION -DICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_FILE -DUCHAR_TYPE=uint16_t -I../.. -Igen -I../../third_party/freetype/include -I../../third_party/freetype/src/include -I../../third_party/harfbuzz-ng/src/src -I../../third_party/icu/source/common -I../../third_party/icu/source/i18n -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -funwind-tables -fPIC -B../../third_party/binutils/Linux_x64/Release/bin -pthread -fcolor-diagnostics -fmerge-all-constants -Xclang -mllvm -Xclang -instcombine-lower-dbg-declare=0 -no-canonical-prefixes -fcomplete-member-pointers -m64 -march=x86-64 -fno-omit-frame-pointer -g0 -fvisibility=hidden -Xclang -load -Xclang ../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang enforce-in-thirdparty-webkit -Xclang -plugin-arg-find-bad-constructs -Xclang check-enum-max-value -Xclang -plugin-arg-find-bad-constructs -Xclang check-ipc -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Werror -Wall -Wno-unused-variable -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-unneeded-internal-declaration -Wno-undefined-var-template -Wno-null-pointer-arithmetic -Wno-ignored-pragma-optimize -Wno-unused-value -Wno-unused-local-typedef -O3 -fno-ident -fdata-sections -ffunction-sections -isystem../../build/linux/debian_sid_amd64-sysroot/usr/include/glib-2.0 -isystem../../build/linux/debian_sid_amd64-sysroot/usr/lib/x86_64-linux-gnu/glib-2.0/include -std=c++14 -fno-exceptions -fno-rtti -nostdinc++ -isystem../../buildtools/third_party/libc++/trunk/include -isystem../../buildtools/third_party/libc++abi/trunk/include --sysroot=../../build/linux/debian_sid_amd64-sysroot -fvisibility-inlines-hidden -c ../../third_party/harfbuzz-ng/src/src/hb-ot-cff1-table.cc -o obj/third_party/harfbuzz-ng/harfbuzz_source/hb-ot-cff1-table.o
In file included from ../../third_party/harfbuzz-ng/src/src/hb-ot-cff1-table.cc:27:
../../third_party/harfbuzz-ng/src/src/hb-ot-cff1-table.hh:676:3: error: control may reach end of non-void function [-Werror,-Wreturn-type]
  }
  ^
1 error generated.

Thanks in advance for taking a look, @blueshade7 .

[ebraminio]

Is the landed fix by @blueshade7 is enough? I wonder how our -Weverything bot https://github.com/harfbuzz/harfbuzz/blob/master/.circleci/config.yml#L140 didn't catch it.

[ebraminio]

The linked compiler log suggests the fix will be enough, Chromium however shouldn't use CFF's get_extents till all its fuzz discovered bugs be fixed, or, these lines should be commented.