I'm seeing the current fuzzer build fail (during `cmake`) like so:
```
-- Performing Test IS_FSANITIZE_FUZZER_NO_LINK_SUPPORTED
-- Performing Test IS_FSANITIZE_FUZZER_NO_LINK_SUPPORTED - Failed
CMake Error at cmake/AddCFlagIfSupported.cmake:17 (message):
Required flag -fsanitize=fuzzer-no-link is not supported
Call Stack (most recent call first):
fuzzers/CMakeLists.txt:6 (add_c_flag)
```
The cmake log output contains something like so:
```
/src/aflplusplus/libAFLDriver.a(aflpp_driver.o): in function `main':
aflpp_driver.c:(.text+0x11b): undefined reference to `LLVMFuzzerTestOneInput'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```
I haven't figured out exactly what's happening, but I believe that
once line 5 has added `-fsanitize=fuzzer` to `CFLAGS`, future compile-
tests **also** use it during linking. This in turn pulls in the fuzzer
`main`, which expects an `LLVMFuzzerTestOneInput` symbol, and thus
fails.
Instead, just add `-fsanitize=fuzzer-no-link` to CFLAGS (as suggested
[by the documentation][libfuzzer]), and then use `-fsanitize=fuzzer`
only for linking the fuzzer targets. At least in my environment, this
results in a working fuzzer build.
[libfuzzer]: https://llvm.org/docs/LibFuzzer.html#fuzzer-usage
Some benchmarks require administrative privileges, namely the ones that
blow up the disk cache. Don't run them by default, to avoid obnoxious
sudo password prompts, etc. Users can specify `--admin` to run them.
The default in the world is to have a disk cache; it's exceptional to
_not_. Flip our naming, so that the (exceptional) `nocache` tests are
called out explicitly.
I tried to build my libgit2-1.9.0 package for CYGWIN but I got an error. This message appears when compiling:
[199/671] Building C object src/cli/CMakeFiles/git2_cli.dir/opt.c.o
libgit2-1.9.0/src/cli/opt.c: In function ‘cli_opt_parse’:
libgit2-1.9.0/src/cli/opt.c:564:23: warning: implicit declaration of function ‘alloca’; did you mean ‘malloc’? [-Wimplicit-function-declaration]
564 | given_specs = alloca(sizeof(const cli_opt_spec *) * (args_len + 1));
| ^~~~~~
| malloc
and later the linker emits this error message:
[668/671] Linking C executable git2.exe
FAILED: git2.exe
/usr/x86_64-pc-cygwin/bin/ld: src/cli/CMakeFiles/git2_cli.dir/opt.c.o: in function `cli_opt_parse':
/usr/src/debug/libgit2-1.9.0-1/src/cli/opt.c:564:(.text+0xce3): undefined reference to `alloca'
collect2: error: ld returned 1 exit status
The error is fixed by adding alloca.h to included headers.
Hopefully, opt.c already allows to add alloca.h for some platforms, so I just added an additional test for the preprocessor for checking if the target is CYGWIN.
Introduce `--profile` support to the benchmark helper script, which will
invoke `perf` on Linux. Additionally, add a `--flamegraph` output
option based on that.
It can be useful to report the commit ID during benchmarks to track down
regressions; leverage the addition of that in `git version` during
benchmark runs.
