Default WITH_TEST_FUZZ to OFF

[steven-johnson]

Just because our compiler supports fuzzing doesn't mean we want to build the fuzz tests, because they won't really build properly without the right preset specified.

(This will be followed up with a change to the buildbot to set WITH_TEST_FUZZ to ON for fuzz tests)

attn: @TH3CHARLie

[TH3CHARLie]

want to add to the reasons for not enabling them by default, with fuzzer linked, whenever you call f.realize you will get something like this:

Internal Error at /home/xuanda/dev/Serializer/Halide/src/JITModule.cpp:226 triggered by user code at : Condition failed: addr: Failed to materialize symbols: { (main, { blur_y_metadata, blur_y, $.blur_y.__inits.0, __orc_init_func.blur_y, sancov.module_ctor_8bit_counters, blur_y_argv }) }

Not sure about the exact reason, but most likely because libfuzz will insert some kind of main into the code already.

[steven-johnson]

Monday morning review ping

[alexreinking]

What doesn't work, exactly? The idea was that HAS_FUZZ_FLAGS was a sufficient condition on the environment for the fuzz tests to be expected to work. What is the true condition?

[steven-johnson]

What doesn't work, exactly? The idea was that HAS_FUZZ_FLAGS was a sufficient condition on the environment for the fuzz tests to be expected to work. What is the true condition?

The fuzzer tests must be built using the linux-x64-fuzzer preset

[alexreinking]

The fuzzer tests must be built using the linux-x64-fuzzer preset

That's kind of my question... why? What does the preset do that's special? The only non-standard thing I see is that it uses static Halide (so BUILD_SHARED_LIBS=OFF),

[TH3CHARLie]

The fuzzer tests must be built using the linux-x64-fuzzer preset

That's kind of my question... why? What does the preset do that's special? The only non-standard thing I see is that it uses static Halide (so BUILD_SHARED_LIBS=OFF),

I believe it's the new flag making it special:

Halide/cmake/toolchain.linux-x64-fuzzer.cmake

Lines 20 to 25 in fd9bfc8

	set(CMAKE_C_FLAGS_INIT "-fsanitize=fuzzer-no-link")
	set(CMAKE_CXX_FLAGS_INIT "-fsanitize=fuzzer-no-link")
	set(CMAKE_EXE_LINKER_FLAGS_INIT "-fuse-ld=${CMAKE_LINKER}")
	set(CMAKE_MODULE_LINKER_FLAGS_INIT "-fuse-ld=${CMAKE_LINKER}")
	set(CMAKE_SHARED_LINKER_FLAGS_INIT "-fuse-ld=${CMAKE_LINKER}")

[steven-johnson]

Yep, -fsanitize=fuzzer-no-link dramatically affects codegen

[abadams]

e.g. it injects its own int main!