tree-wide: add SD_ID128_MAKE_STR, remove LOG_MESSAGE_ID

Embedding sd_id128_t's in constant strings was rather cumbersome. We had
SD_ID128_CONST_STR which returned a const char[], but it had two problems:
- it wasn't possible to statically concatanate this array with a normal string
- gcc wasn't really able to optimize this, and generated code to perform the
  "conversion" at runtime.
Because of this, even our own code in coredumpctl wasn't using
SD_ID128_CONST_STR.

Add a new macro to generate a constant string: SD_ID128_MAKE_STR.
It is not as elegant as SD_ID128_CONST_STR, because it requires a repetition
of the numbers, but in practice it is more convenient to use, and allows gcc
to generate smarter code:

$ size .libs/systemd{,-logind,-journald}{.old,}
   text	   data	    bss	    dec	    hex	filename
1265204	 149564	   4808	1419576	 15a938	.libs/systemd.old
1260268	 149564	   4808	1414640	 1595f0	.libs/systemd
 246805	  13852	    209	 260866	  3fb02	.libs/systemd-logind.old
 240973	  13852	    209	 255034	  3e43a	.libs/systemd-logind
 146839	   4984	     34	 151857	  25131	.libs/systemd-journald.old
 146391	   4984	     34	 151409	  24f71	.libs/systemd-journald

It is also much easier to check if a certain binary uses a certain MESSAGE_ID:

$ strings .libs/systemd.old|grep MESSAGE_ID
MESSAGE_ID=%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x
MESSAGE_ID=%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x
MESSAGE_ID=%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x
MESSAGE_ID=%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x

$ strings .libs/systemd|grep MESSAGE_ID
MESSAGE_ID=c7a787079b354eaaa9e77b371893cd27
MESSAGE_ID=b07a249cd024414a82dd00cd181378ff
MESSAGE_ID=641257651c1b4ec9a8624d7a40a9e1e7
MESSAGE_ID=de5b426a63be47a7b6ac3eaac82e2f6f
MESSAGE_ID=d34d037fff1847e6ae669a370e694725
MESSAGE_ID=7d4958e842da4a758f6c1cdc7b36dcc5
MESSAGE_ID=1dee0369c7fc4736b7099b38ecb46ee7
MESSAGE_ID=39f53479d3a045ac8e11786248231fbf
MESSAGE_ID=be02cf6855d2428ba40df7e9d022f03d
MESSAGE_ID=7b05ebc668384222baa8881179cfda54
MESSAGE_ID=9d1aaa27d60140bd96365438aad20286

1 files changed, 14 insertions, 1 deletions

diff --git a/man/sd-id128.xml b/man/sd-id128.xml
index 5f24feff8e..2e29cf91cb 100644
--- a/man/sd-id128.xml
+++ b/man/sd-id128.xml
@@ -47,6 +47,7 @@
     <refname>sd-id128</refname>
     <refname>sd_id128_t</refname>
     <refname>SD_ID128_MAKE</refname>
+    <refname>SD_ID128_MAKE_STR</refname>
     <refname>SD_ID128_NULL</refname>
     <refname>SD_ID128_CONST_STR</refname>
     <refname>SD_ID128_FORMAT_STR</refname>
@@ -113,12 +114,24 @@
     <para><function>SD_ID128_NULL</function> may be used to refer to the 128bit ID consisting of only NUL
     bytes.</para>
 
+    <para><function>SD_ID128_MAKE_STR()</function> is similar to <function>SD_ID128_MAKE()</function>, but creates a
+    <type>const char*</type> expression that can be conveniently used in message formats and such:</para>
+
+    <programlisting>#include &lt;stdio.h&gt;
+#define SD_MESSAGE_COREDUMP_STR SD_ID128_MAKE_STR(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1)
+
+int main(int argc, char **argv) {
+        puts("Match for coredumps: MESSAGE_ID=" SD_MESSAGE_COREDUMP_STR);
+}
+    </programlisting>
+
+
     <para><function>SD_ID128_CONST_STR()</function> may be used to
     convert constant 128-bit IDs into constant strings for output. The
     following example code will output the string
     "fc2e22bc6ee647b6b90729ab34a250b1":</para>
     <programlisting>int main(int argc, char *argv[]) {
-        puts(SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP));
+        puts("Match for coredumps: %s", SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP));
 }</programlisting>
 
     <para><function>SD_ID128_FORMAT_STR()</function> and