commit b1811b31f3a99da5dbb1c9cef7db4a14e7f6154d
author Patrick Williams <patrick@stwcx.xyz> Thu Aug 26 12:19:01 2021 -0500
committer Patrick Williams <patrick@stwcx.xyz> Mon Aug 30 21:54:49 2021 +0000
tree 438e34611cb7b0f46ab75dc81df523d90241cd35
parent b5988ff8eddffa8513ce276b1a81af36c4abe5b0

lg2: minor size optimization in do_log

Push the calculation of the number of logging arguments into the
variadic 'do_log' function rather than calculate it at the lg2
call site.  This reduces each call site by a few instructions.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ic8fcbdf65fb34d251d8110c5bbd05c2e20c66c18

lib/lg2_logger.cpp

diff --git a/lib/lg2_logger.cpp b/lib/lg2_logger.cpp
index ac7a75c..fd3921c 100644
--- a/lib/lg2_logger.cpp
+++ b/lib/lg2_logger.cpp
@@ -143,13 +143,11 @@
     isatty(fileno(stderr)) ? cerr_extra_output : noop_extra_output;
 
 // Do_log implementation.
-void do_log(level l, const std::source_location& s, const char* m, size_t count,
-            ...)
+void do_log(level l, const std::source_location& s, const char* m, ...)
 {
     using namespace std::string_literals;
 
-    const size_t entries = count + static_locs;
-    std::vector<std::string> strings{entries};
+    std::vector<std::string> strings{static_locs};
 
     std::string message{m};
 
@@ -162,11 +160,16 @@
 
     // Handle all the va_list args.
     std::va_list args;
-    va_start(args, count);
-    for (size_t i = static_locs; i < entries; ++i)
+    va_start(args, m);
+    while (true)
     {
         // Get the header out.
-        std::string h = va_arg(args, const char*);
+        auto h_ptr = va_arg(args, const char*);
+        if (h_ptr == nullptr)
+        {
+            break;
+        }
+        std::string h{h_ptr};
 
         // Get the format flag.
         auto f = va_arg(args, uint64_t);
@@ -204,7 +207,7 @@
         }
 
         // Create the field for this value.
-        strings[i] = h + '=' + value;
+        strings.emplace_back(h + '=' + value);
 
         // Check for {HEADER} in the message and replace with value.
         auto h_brace = '{' + h + '}';
@@ -225,7 +228,7 @@
     });
 
     // Output the iovec.
-    sd_journal_sendv(iov.data(), entries);
+    sd_journal_sendv(iov.data(), strings.size());
     extra_output_method(l, s, message);
 }