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

[Pavel Labath via libc-commits]

================
@@ -1,3 +1,73 @@
+# Unified CMake diagnostic logging configuration.
+# Levels for LIBC_CMAKE_VERBOSE_LOGGING:
+#   OFF:          Quiet configure (only summary, warnings, and errors).
+#   ON / BASIC:   Skipped entrypoints/tests/suites, config overrides, alias fallbacks.
+#   TARGETS:      Includes BASIC, plus target creation across all rules, alias chains, and flag variants.
+#   DEPS:         Includes TARGETS, plus full dependency DAG, flag projection, and argument overrides.
+set(LIBC_CMAKE_VERBOSE_LOGGING "OFF" CACHE STRING
+  "Verbose CMake logging level: OFF, ON (or BASIC), TARGETS, DEPS."
+)
+set(LIBC_CMAKE_VERBOSE_TARGET_FILTER "" CACHE STRING
+  "Optional regex filter restricting TARGETS and DEPS logging to matching target names."
+)
+
+if(NOT LIBC_CMAKE_VERBOSE_LOGGING)
+  set(_LIBC_LOG_LEVEL 0)
+elseif(LIBC_CMAKE_VERBOSE_LOGGING STREQUAL "DEPS")
+  set(_LIBC_LOG_LEVEL 3)
+elseif(LIBC_CMAKE_VERBOSE_LOGGING STREQUAL "TARGETS")
+  set(_LIBC_LOG_LEVEL 2)
+else()
+  set(_LIBC_LOG_LEVEL 1)
+endif()
+
+function(_libc_log_impl level)
+  if(level STREQUAL "DEPS")
+    set(req_level 3)
+  elseif(level STREQUAL "TARGETS")
+    set(req_level 2)
+  else()
+    set(req_level 1)
+  endif()
+
+  if(_LIBC_LOG_LEVEL LESS req_level)
+    return()
+  endif()
+
+  set(msg_args ${ARGN})
+  set(filter_subject "")
+  list(LENGTH msg_args num_args)
+  if(num_args GREATER_EQUAL 2)
+    list(GET msg_args 0 first_arg)
+    if(first_arg STREQUAL "TARGET")
+      list(GET msg_args 1 filter_subject)
+      list(REMOVE_AT msg_args 0 1)
+    endif()
+  endif()
+
+  string(JOIN "" msg_text ${msg_args})
+  if(LIBC_CMAKE_VERBOSE_TARGET_FILTER)
+    if(NOT filter_subject)
+      set(filter_subject "${msg_text}")
+    endif()
+    if(NOT "${filter_subject}" MATCHES "${LIBC_CMAKE_VERBOSE_TARGET_FILTER}")
+      return()
+    endif()
+  endif()
+
+  message(STATUS "${msg_text}")
+endfunction()
+
+# Unified CMake diagnostic logger.
+# Usage:
+#   libc_log(<LEVEL> [TARGET <target_name>] <message>...)
+macro(libc_log _libc_log_level)
----------------
labath wrote:

What's the point of the wrapper? Is it actually faster than letting the function bail out at the `  if(_LIBC_LOG_LEVEL LESS req_level)` line? Or adding an early exit at the beginning of the function?

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