Compilation failure with Clang on Windows

[aminya]

Problem:

When building with Clang on Windows, the compilation first fails with the following error

  exit code: 1
  cargo:warning=ToolExecError: command did not execute successfully (status code exit code: 1): "C:/ProgramData/chocolatey/bin/sccache.exe" "C:\\Users\\aminya\\llvm/bin/clang.exe" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-g" "-fno-omit-frame-pointer" "-m64" "--target=x86_64-pc-windows-msvc" "-I" "O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\generated-include" "-I" "O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\include" "-I" "O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\aws-lc\\include" "-I" "O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\aws-lc\\third_party\\s2n-bignum\\include" "-I" "O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\aws-lc\\third_party\\s2n-bignum\\s2n-bignum-imported\\include" "-I" "O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\aws-lc\\third_party\\jitterentropy\\jitterentropy-library" "-Wall" "-Wextra" "-fwrapv" "--param" "ssp-buffer-size=4" "-fvisibility=hidden" "-Wcast-align" "-Wmissing-field-initializers" "-Wshadow" "-Wswitch-enum" "-Wextra" "-Wall" "-pedantic" "-O0" "-fwrapv" "-Wconversion" "--include=O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\generated-include\\openssl\\boringssl_prefix_symbols.h" "-DBORINGSSL_IMPLEMENTATION=1" "-DBORINGSSL_PREFIX=aws_lc_0_37_0" "-DWIN32_LEAN_AND_MEAN=" "-DNOMINMAX=" "-DAWSLC=1" "-o" "O:\\GitHub\\aws-lc-rs\\target\\debug\\build\\aws-lc-sys-6f422e044d29205d\\out\\307a1cf338c197ca-jitterentropy-gcd.o" "-c" "O:\\GitHub\\aws-lc-rs\\aws-lc-sys\\aws-lc\\third_party/jitterentropy/jitterentropy-library/src/jitterentropy-gcd.c"cargo:warning=clang: error: unsupported option '-fPIC' for target 'x86_64-pc-windows-msvc'
  cargo:warning=clang: error: unsupported option '-fPIC' for target 'x86_64-pc-windows-msvc'

If that is fixed, then the following upstream error happens

aws/aws-lc#2981

FAILED: aws-lc/crypto/fipsmodule/bcm.o O:/GitHub/aws-lc-rs/target/debug/build/aws-lc-fips-sys-dc904e8765dea6e9/out/build/aws-lc/crypto/fipsmodule/bcm.o 
C:\Windows\System32\cmd.exe /C "cd /D O:\GitHub\aws-lc-rs\target\debug\build\aws-lc-fips-sys-dc904e8765dea6e9\out\build\aws-lc\crypto\fipsmodule && C:\Users\aminya\llvm\bin\lld-link.exe -r -T O:/GitHub/aws-lc-rs/aws-lc-fips-sys/aws-lc/crypto/fipsmodule/fips_shared.lds -o bcm.o --whole-archive O:/GitHub/aws-lc-rs/target/debug/build/aws-lc-fips-sys-dc904e8765dea6e9/out/build/aws-lc/crypto/fipsmodule/bcm_library.lib"
lld-link: warning: ignoring unknown argument '-r'
lld-link: warning: ignoring unknown argument '-T'
lld-link: warning: ignoring unknown argument '-o'
lld-link: warning: ignoring unknown argument '--whole-archive'
lld-link: error: O:/GitHub/aws-lc-rs/aws-lc-fips-sys/aws-lc/crypto/fipsmodule/fips_shared.lds: unknown file type
lld-link: error: could not open 'bcm.o': no such file or directory
ninja: build stopped: subcommand failed.

Relevant details

AWS-LC-RS commit: 7501783

System information:

• CPU architecture: x86
• CPU name: AMD
• OS: Windows 11

Build log:

• The log tells compiler and version. It's available when building awslc with CMake.

> cmake "--build" "O:\\GitHub\\aws-lc-rs\\target\\debug\\build\\aws-lc-fips-sys-dc904e8765dea6e9\\out\\build" "--target" "install" "--config" "Debug" "--parallel" "32"

[0/1] Re-running CMake...CMake Deprecation Warning at CMakeLists.txt:10 (cmake_policy):
  The OLD behavior for policy CMP0091 will be removed from a future version
  of CMake.

  The cmake-policies(7) manual explains that the OLD behaviors of all
  policies are deprecated and that a policy should be set to OLD only under
  specific short-term circumstances.  Projects should be ported to the NEW
  behavior and not rely on setting a policy to OLD.


-- Go compiler 1.25.6 found
-- ENABLE_PRE_SONAME_BUILD: ON
-- PERFORM_SONAME_BUILD: 0
-- Entropy source configured: Dynamic (default: CPU Jitter)
-- Prefix build configured: performing build using prefix "aws_lc_fips_0_13_11_" and headers path "O:\GitHub\aws-lc-rs\aws-lc-fips-sys\generated-include"
-- Setting CMAKE_C_STANDARD=11
-- Performing Test HAVE_C_FLAG__Wno_cast_function_type
-- Performing Test HAVE_C_FLAG__Wno_cast_function_type - Success
-- Compiler supports '-Wno-cast-function-type', adding to CMAKE_C_FLAGS
-- Performing Test HAVE_C_FLAG__Wstring_concatenation
-- Performing Test HAVE_C_FLAG__Wstring_concatenation - Success
-- Compiler supports '-Wstring-concatenation', adding to C_CXX_FLAGS
-- Performing Test HAVE_C_FLAG__Wimplicit_fallthrough
-- Performing Test HAVE_C_FLAG__Wimplicit_fallthrough - Success
-- Compiler supports '-Wimplicit-fallthrough', adding to C_CXX_FLAGS
-- linux_random_h.c probe is negative, NOT enabling HAVE_LINUX_RANDOM_H:
-- Use -DFEATURE_PROBE_VERBOSE=ON to view feature probe error output.
-- linux_random_h.c probe is negative, NOT enabling AWS_LC_URANDOM_NEEDS_U32:
-- Use -DFEATURE_PROBE_VERBOSE=ON to view feature probe error output.
-- stdalign_check.c probe is positive, enabling AWS_LC_STDALIGN_AVAILABLE
-- builtin_swap_check.c probe is positive, enabling AWS_LC_BUILTIN_SWAP_SUPPORTED
-- Performing Test HAVE_C_FLAG__Wshadow
-- Performing Test HAVE_C_FLAG__Wshadow - Success
-- Compiler supports '-Wshadow', adding to C_CXX_FLAGS
-- Configuring done (2.0s)
-- Generating done (0.1s)

...

FAILED: aws-lc/crypto/fipsmodule/bcm.o O:/GitHub/aws-lc-rs/target/debug/build/aws-lc-fips-sys-dc904e8765dea6e9/out/build/aws-lc/crypto/fipsmodule/bcm.o 
C:\Windows\System32\cmd.exe /C "cd /D O:\GitHub\aws-lc-rs\target\debug\build\aws-lc-fips-sys-dc904e8765dea6e9\out\build\aws-lc\crypto\fipsmodule && C:\Users\aminya\llvm\bin\lld-link.exe -r -T O:/GitHub/aws-lc-rs/aws-lc-fips-sys/aws-lc/crypto/fipsmodule/fips_shared.lds -o bcm.o --whole-archive O:/GitHub/aws-lc-rs/target/debug/build/aws-lc-fips-sys-dc904e8765dea6e9/out/build/aws-lc/crypto/fipsmodule/bcm_library.lib"
lld-link: warning: ignoring unknown argument '-r'
lld-link: warning: ignoring unknown argument '-T'
lld-link: warning: ignoring unknown argument '-o'
lld-link: warning: ignoring unknown argument '--whole-archive'
lld-link: error: O:/GitHub/aws-lc-rs/aws-lc-fips-sys/aws-lc/crypto/fipsmodule/fips_shared.lds: unknown file type
lld-link: error: could not open 'bcm.o': no such file or directory
ninja: build stopped: subcommand failed.

[justsmth]

Hello!

You're right. The "-fPIC" should not be set for Windows. The AWS-LC build configuration only sets CMAKE_POSITION_INDEPENDENT_CODE when not on Windows.

Thanks for the issue and PR!