[libc-commits] [libc] [libc][cmake] Fix and enhance LibcParseArguments and add unified libc_log helper (PR #232089)

[Pavel Labath via libc-commits]

================
@@ -1,17 +1,127 @@
+# This file provides a unified argument parsing facility for LLVM-libc CMake
+# rules (such as add_libc_test, create_libc_test, add_entrypoint_object, etc.).
+#
+# Every argument declared in `LLVM_LIBC_OPTIONAL_ARGS`,
+# `LLVM_LIBC_SINGLE_VALUE_ARGS`, or `LLVM_LIBC_MULTI_VALUE_ARGS` automatically
+# receives two mode-specific variants:
+#   OVERLAY_<arg>
+#   FULL_BUILD_<arg>
+#
+# When `llvm_libc_parse_arguments` is called:
+#   1. It parses all base, overlay, and full-build argument variants using
+#      cmake_parse_arguments.
+#   2. It determines the active build mode (either explicitly specified via
+#      `BUILD_MODE` or defaulted from `LLVM_LIBC_FULL_BUILD`).
+#   3. It automatically merges the active mode's argument values
+#      (e.g., `FULL_BUILD_<arg>` or `OVERLAY_<arg>`) into the canonical
+#      `<prefix>_<arg>` variable.
+#
+# Examples:
+#
+# 1. Mode-specific dependencies or compile options:
+#
+#      add_libc_test(
+#        sin_test
+#        SUITE libc_math_tests
+#        SRCS sin_test.cpp
+#        DEPENDS libc.src.math.sin
+#        OVERLAY_DEPENDS libc.test.UnitTest.OverlaySupport
+#        FULL_BUILD_DEPENDS libc.test.UnitTest.HermeticSupport
+#        FULL_BUILD_COMPILE_OPTIONS -ffreestanding
+#      )
+#
+#    - In overlay mode (LLVM_LIBC_FULL_BUILD=OFF):
+#        TEST_DEPENDS will contain:
+#          libc.src.math.sin;libc.test.UnitTest.OverlaySupport
+#
+#    - In full-build mode (LLVM_LIBC_FULL_BUILD=ON):
+#        TEST_DEPENDS will contain:
+#          libc.src.math.sin;libc.test.UnitTest.HermeticSupport
+#        TEST_COMPILE_OPTIONS will contain:
+#          -ffreestanding
+#
+# 2. Mode-restricted targets:
+#
+#      add_libc_test(
+#        loader_test
+#        FULL_BUILD_ONLY
+#        SUITE libc_loader_tests
+#        SRCS loader_test.cpp
+#        DEPENDS ...
+#      )
+#
+#    - When parsed in overlay mode:
+#        TEST_FULL_BUILD_ONLY evaluates to TRUE, allowing the caller to
+#        skip defining the target. Similarly, `OVERLAY_ONLY` skips the
+#        target in full-build mode.
+#
+# 3. Explicit BUILD_MODE override:
+#
+#      add_libc_test(
+#        gpu_perf
+#        IS_GPU_BENCHMARK
+#        BUILD_MODE FULL_BUILD
+#        SRCS perf.cpp
+#        DEPENDS ...
+#      )
+#
+#    - Even if LLVM_LIBC_FULL_BUILD is OFF, `BUILD_MODE FULL_BUILD` ensures
+#      that full-build rules and FULL_BUILD_* options are selected.
+#
+# 4. Forwarding merged arguments:
+#
+#    `forward_arguments(name_prefix output_var)` re-emits only the canonical
+#    (merged) arguments, dropping the mode-specific prefixes. This allows
+#    outer wrapper functions to pass fully-resolved arguments down to inner
+#    rules without repeating mode resolution:
+#
+#      function(add_libc_test test_name)
+#        llvm_libc_parse_arguments(LIBC_TEST ${ARGN})
+#        ...
+#        forward_arguments(LIBC_TEST forwarded_args)
+#        _add_libc_test(${test_name} ${forwarded_args} ${LIBC_TEST_UNPARSED_ARGUMENTS})
+#      endfunction()
+
+# Common options that control mode / target inclusion. These do NOT receive
+# OVERLAY_ or FULL_BUILD_ prefixes.
+set(LLVM_LIBC_COMMON_OPTIONAL_ARGS
+  FULL_BUILD_ONLY
+  OVERLAY_ONLY
+)
+
+set(LLVM_LIBC_COMMON_SINGLE_VALUE_ARGS
+  BUILD_MODE
----------------
labath wrote:

What's the use case for this? I mean, as far as this code is concerned, this is fine, but I'm worried about the big picture. Trying to mix targets built with different modes in the same build sounds like a bad idea to me.

https://github.com/llvm/llvm-project/pull/232089