pw_log: Remove uses of PW_COMMA_ARGS

- Remove uses of PW_COMMA_ARGS on macro-macro boundaries. PW_COMMA_ARGS
  doesn't expand as expected when invoking one macro from another.
- Expand comment for PW_COMMA_ARGS to indicate that it should not be
  used when invoking a macro from another macro. It should only be used
  when the macro expands to C code (e.g. a function call).

Bug: 117
Change-Id: I201197f0b4727304cc2dedad40ed2f5b6d02b27e

pw_log/BUILD.gn

diff --git a/pw_log/BUILD.gn b/pw_log/BUILD.gn
index 9216bf4..1dbe783 100644
--- a/pw_log/BUILD.gn
+++ b/pw_log/BUILD.gn
@@ -27,7 +27,6 @@
     "public/pw_log/levels.h",
     "public/pw_log/log.h",
   ]
-  public_deps = [ dir_pw_preprocessor ]
 }
 
 pw_test_group("tests") {
@@ -42,6 +41,7 @@
     deps = [
       ":pw_log",
       dir_pw_log_backend,
+      dir_pw_preprocessor,
     ]
 
     sources = [

pw_log/public/pw_log/log.h

diff --git a/pw_log/public/pw_log/log.h b/pw_log/public/pw_log/log.h
index 97db527..66203a8 100644
--- a/pw_log/public/pw_log/log.h
+++ b/pw_log/public/pw_log/log.h
@@ -26,7 +26,6 @@
 #pragma once
 
 #include "pw_log/levels.h"
-#include "pw_preprocessor/macro_arg_count.h"  // PW_COMMA_ARGS
 
 // log_backend.h must ultimately resolve to a header that implements the macros
 // required by the logging facade, as described below.
@@ -76,31 +75,27 @@
 // of the general PW_LOG().
 #ifndef PW_LOG_DEBUG
 #define PW_LOG_DEBUG(message, ...) \
-  PW_LOG(                          \
-      PW_LOG_LEVEL_DEBUG, PW_LOG_NO_FLAGS, message PW_COMMA_ARGS(__VA_ARGS__))
+  PW_LOG(PW_LOG_LEVEL_DEBUG, PW_LOG_NO_FLAGS, message, __VA_ARGS__)
 #endif  // PW_LOG_DEBUG
 
 #ifndef PW_LOG_INFO
 #define PW_LOG_INFO(message, ...) \
-  PW_LOG(PW_LOG_LEVEL_INFO, PW_LOG_NO_FLAGS, message PW_COMMA_ARGS(__VA_ARGS__))
+  PW_LOG(PW_LOG_LEVEL_INFO, PW_LOG_NO_FLAGS, message, __VA_ARGS__)
 #endif  // PW_LOG_INFO
 
 #ifndef PW_LOG_WARN
 #define PW_LOG_WARN(message, ...) \
-  PW_LOG(PW_LOG_LEVEL_WARN, PW_LOG_NO_FLAGS, message PW_COMMA_ARGS(__VA_ARGS__))
+  PW_LOG(PW_LOG_LEVEL_WARN, PW_LOG_NO_FLAGS, message, __VA_ARGS__)
 #endif  // PW_LOG_WARN
 
 #ifndef PW_LOG_ERROR
 #define PW_LOG_ERROR(message, ...) \
-  PW_LOG(                          \
-      PW_LOG_LEVEL_ERROR, PW_LOG_NO_FLAGS, message PW_COMMA_ARGS(__VA_ARGS__))
+  PW_LOG(PW_LOG_LEVEL_ERROR, PW_LOG_NO_FLAGS, message, __VA_ARGS__)
 #endif  // PW_LOG_ERROR
 
 #ifndef PW_LOG_CRITICAL
 #define PW_LOG_CRITICAL(message, ...) \
-  PW_LOG(PW_LOG_LEVEL_CRITICAL,       \
-         PW_LOG_NO_FLAGS,             \
-         message PW_COMMA_ARGS(__VA_ARGS__))
+  PW_LOG(PW_LOG_LEVEL_CRITICAL, PW_LOG_NO_FLAGS, message, __VA_ARGS__)
 #endif  // PW_LOG_CRITICAL
 
 // Define short, usable names if requested.

pw_log_basic/BUILD.gn

diff --git a/pw_log_basic/BUILD.gn b/pw_log_basic/BUILD.gn
index d5a9dd8..f5b8758 100644
--- a/pw_log_basic/BUILD.gn
+++ b/pw_log_basic/BUILD.gn
@@ -30,7 +30,6 @@
     ]
     deps = [ ":pw_log_basic_core" ]
     public = [ "public_overrides/pw_log_backend/log_backend.h" ]
-    sources = public
   }
 }
 
@@ -43,6 +42,7 @@
     "$dir_pw_sys_io",
   ]
   public = [ "public/pw_log_basic/log_basic.h" ]
+  public_deps = [ dir_pw_preprocessor ]
 
   # Use emoji log levels if they've been enabled.
   _use_emoji = getenv("PW_EMOJI")
@@ -51,7 +51,7 @@
     defines += [ "PW_EMOJI=1" ]
   }
 
-  sources = public + [ "log_basic.cc" ]
+  sources = [ "log_basic.cc" ]
 }
 
 pw_doc_group("docs") {

pw_log_basic/public/pw_log_basic/log_basic.h

diff --git a/pw_log_basic/public/pw_log_basic/log_basic.h b/pw_log_basic/public/pw_log_basic/log_basic.h
index e820921..305b786 100644
--- a/pw_log_basic/public/pw_log_basic/log_basic.h
+++ b/pw_log_basic/public/pw_log_basic/log_basic.h
@@ -14,6 +14,7 @@
 #pragma once
 
 #include "pw_preprocessor/compiler.h"
+#include "pw_preprocessor/macro_arg_count.h"
 #include "pw_preprocessor/util.h"
 
 PW_EXTERN_C_START

pw_preprocessor/public/pw_preprocessor/macro_arg_count.h

diff --git a/pw_preprocessor/public/pw_preprocessor/macro_arg_count.h b/pw_preprocessor/public/pw_preprocessor/macro_arg_count.h
index 8525577..4d704de 100644
--- a/pw_preprocessor/public/pw_preprocessor/macro_arg_count.h
+++ b/pw_preprocessor/public/pw_preprocessor/macro_arg_count.h
@@ -103,13 +103,18 @@
 // Expands to a comma followed by __VA_ARGS__, if __VA_ARGS__ is non-empty.
 // Otherwise, expands to nothing. This is useful when calling a function with
 // __VA_ARGS__, since it removes the extra comma when no arguments are
-// provided.
+// provided. It must NOT be used when invoking a macro from another macro.
 //
 // This is a more flexible, standard-compliant version of ##__VA_ARGS__. Unlike
 // ##__VA_ARGS__, this can be used to eliminate an unwanted comma when
 // __VA_ARGS__ expands to an empty argument because an outer macro was called
 // with __VA_ARGS__ instead of ##__VA_ARGS__.
 //
+// PW_COMMA_ARGS must NOT be used to conditionally include a comma when invoking
+// a macro from another macro. PW_COMMA_ARGS only functions correctly when the
+// macro expands to C or C++ code! When invoking one macro from another, simply
+// pass __VA_ARGS__.
+//
 // This can be used to call variadic functions or provide variadic template
 // parameters from a macro. For example:
 //