[RFC PATCH 14/15] config.mak.dev: add a DEVOPTS=analyzer mode to use GCC's -fanalyzer
- From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
- Date
- Jun 3, 2022, 18:37 UTC
- Message-ID
- <RFC-patch-14.15-9cf550688d4-20220603T183608Z-avarab@gmail.com>
- In-Reply-To
- <RFC-cover-00.15-00000000000-20220603T183608Z-avarab@gmail.com>
Add an option to compile with GCC's -fanalyzer, which as noted in [1] and [2] has become much more useful in the recently released GCC v12 series.
Here we're quieting a few outstanding -fanalyzer issues that require us to use -Wno-error=* on an entire file:
* range-diff.c, because it involves loop variables and would be painfully verbose to instrument with the ASSERT_FOR_FANALYZER() macro introduced in the subsequent commit.
* http-fetch.c and fsmonitor-settings.c, because those aren't issues where we're referencing NULL, and therefore we can't quiet it with an assert().
For non-GCC compilers I considered wrapping the DEVOPTS logic in:
ifneq ($(filter gcc10,$(COMPILER_FEATURES)),) endif
Which would make it OK to specify DEVOPTS=analyzer under other compilers, or on older GCC. But then we'd silently ignore the option on those. Let's instead trust the compiler to error out if it doesn't support -fanalyzer.
There are various limitations and bugs in the analyzer engine, e.g. I filed [3] for a false positive in builtin/merge-file.c before GCC v12 was released, which was subsequently fixed in GCC 12 trunk in [4], but many other issues remain.
1. https://developers.redhat.com/articles/2022/04/12/state-static-analysis-gcc-12-compiler 2. https://gcc.gnu.org/gcc-12/changes.html 3. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105264 4. https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=a358e4b60815b41e27f3508014ceb592f86b9b45
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> --- Makefile | 14 ++++++++++++ config.mak.dev | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 75 insertions(+)
diff --git a/Makefile b/Makefile index 18ca6744a50..129d55f5992 100644 --- a/Makefile +++ b/Makefile @@ -507,6 +507,20 @@ include shared.mak # no-pedantic: # # Disable -pedantic compilation. +# +# analyzer: +# +# Compile with GCC's -fanalyzer, this analysis is much more +# expensive than other GCC warnings. +# +# The set of analysis flags is curated based on known issues +# and compiler version. Known issues are made into non-fatal +# warnings (even "no-error" isn't set). +# +# no-suppress-analyzer: +# +# When using "analyzer" disable the suppression of known +# -fanalyzer issues. GIT-VERSION-FILE: FORCE @$(SHELL_PATH) ./GIT-VERSION-GEN diff --git a/config.mak.dev b/config.mak.dev index c3104f400b2..d6f5be92297 100644 --- a/config.mak.dev +++ b/config.mak.dev @@ -72,3 +72,64 @@ DEVELOPER_CFLAGS += -Wno-error=dangling-pointer endif GIT_TEST_PERL_FATAL_WARNINGS = YesPlease + +# GCC's -fanalyzer mode +ifeq ($(filter analyzer,$(DEVOPTS)),analyzer) + +ifeq ($(filter gcc1,$(COMPILER_FEATURES)),) +$(error you must be using a new-ish version of GCC for DEVOPTS=analyzer, your \ +$(CC) is not GCC at all!) +endif + +DEVELOPER_CFLAGS += -fanalyzer + +## -fanalyzer exists exists as of gcc10, but versions older than gcc12 +## have a lot of false positives. +ifeq ($(filter gcc12,$(COMPILER_FEATURES)),) +DEVELOPER_CFLAGS += -Wno-analyzer-double-free +DEVELOPER_CFLAGS += -Wno-analyzer-free-of-non-heap +endif + +## Helper templates to whitelist existing issues +define fn_disable_analyzer_tmpl +$(1).sp $(1).s $(1).o: EXTRA_CPPFLAGS += $(2) + +endef + +define fn_disable_analyzer +$(foreach f,$(2),$(call fn_disable_analyzer_tmpl,$(f),$(1))) +endef + +## -Wno-error=analyzer-null-dereference +$(eval $(call fn_disable_analyzer, \ + -Wno-error=analyzer-null-dereference, \ + range-diff \ +)) +## -Wno-error=analyzer-malloc-leak +$(eval $(call fn_disable_analyzer, \ + -Wno-error=analyzer-malloc-leak, \ + fsmonitor-settings \ +)) +## per-GCC version annotations +### -Wno-error=analyzer-use-of-uninitialized-value: gcc >= 12 +ifneq ($(filter gcc12,$(COMPILER_FEATURES)),) +$(eval $(call fn_disable_analyzer, \ + -Wno-error=analyzer-use-of-uninitialized-value, \ + http-fetch \ +)) +else # gcc < 12 +### -Wno-error=analyzer-null-dereference: gcc == 11 +ifneq ($(filter gcc11,$(COMPILER_FEATURES)),) +$(eval $(call fn_disable_analyzer, \ + -Wno-error=analyzer-null-dereference, \ + merge \ + xdiff/xemit \ + reftable/reader \ +)) +else +$(error Your GCC version is too old for -fanalyze, or you are using \ +gcc10 which has it, but has too many false positives!) +endif +endif # gcc < 12 + +endif
-- 2.36.1.1124.g577fa9c2ebd