simplify PERL_MEM_LOG

This combines multiple environment variable reads into 1,
where it looks for values like "2mst"
-2 leading digits are atoi()d to get FD
-m memory logging please
-s sv logging also
-t timestamp those please.

Combining these reduces overhead such that it seemed
worthwhile to drop all the ifdefs.  TBD whether this works
in the environment that drove the original tradeoffs.

If it isnt enough, Id be tempted by a global static ptr,
and on 1st use, is read, seen 0, a lock is taken, and getenvar
run to populate it, unlocked, proceed.  This would remove
iterative overheads.

1 files changed, 24 insertions, 38 deletions

diff --git a/util.c b/util.c
index 22206180e8..d3fe00ac17 100644
--- a/util.c
+++ b/util.c
@@ -5471,34 +5471,29 @@ Perl_free_global_struct(pTHX_ struct perl_vars *plvarsp)
 
 #ifdef PERL_MEM_LOG
 
-/*
- * -DPERL_MEM_LOG: the Perl_mem_log_..() is compiled, including the
+/* -DPERL_MEM_LOG: the Perl_mem_log_..() is compiled, including the
  * the default implementation, unless -DPERL_MEM_LOG_NOIMPL is also
  * given, and you supply your own implementation.
  *
- * -DPERL_MEM_LOG_ENV: if compiled in, at run time the environment
- * variables PERL_MEM_LOG and PERL_SV_LOG are checked (repeatedly).
- * If the integer values are true, the respective logging is done.
- * (Without this also defined, logging is voluminous)
+ * The default implementation reads a single envar; PERL_MEM_LOG,
+ * expecting one or more of the following:
+ *
+ *    \d+ - fd		fd to write to		: must be 1st (atoi)
+ *    'm' - memlog	was PERL_MEM_LOG=1	
+ *    's' - svlog	was PERL_SV_LOG=1
+ *    't' - timestamp	was PERL_MEM_LOG_TIMESTAMP=1
  *
- * -DPERL_MEM_LOG_TIMESTAMP: if compiled, a timestamp will be logged
- * before every memory logging entry. This can be turned off at run
- * time by setting the environment variable PERL_MEM_LOG_TIMESTAMP
- * to zero.
+ * This makes the logger controllable enough that it can reasonably be
+ * added to the system perl.
  */
 
-/*
- * -DPERL_MEM_LOG_SPRINTF_BUF_SIZE=X: size of a (stack-allocated) buffer
+/* -DPERL_MEM_LOG_SPRINTF_BUF_SIZE=X: size of a (stack-allocated) buffer
  * the Perl_mem_log_...() will use (either via sprintf or snprintf).
  */
 #define PERL_MEM_LOG_SPRINTF_BUF_SIZE 128
 
-/*
- * -DPERL_MEM_LOG_FD=2: the file descriptor the Perl_mem_log_...()
- * writes to.  You can also define in compile time
- * PERL_MEM_LOG_ENV_FD, in which case the environment variable
- * PERL_MEM_LOG_FD will be consulted for the file descriptor number to
- * use.
+/* -DPERL_MEM_LOG_FD=N: the file descriptor the Perl_mem_log_...()
+ * writes to.  In the default logger, this is settable at runtime.
  */
 #ifndef PERL_MEM_LOG_FD
 #  define PERL_MEM_LOG_FD 2 /* If STDERR is too boring for you. */
@@ -5521,21 +5516,19 @@ S_mem_log_common(enum mem_log_type mlt, const UV n,
 		 const char *filename, const int linenumber,
 		 const char *funcname)
 {
-# if defined(PERL_MEM_LOG_ENV) || defined(PERL_MEM_LOG_ENV_FD)
-    const char *s;
-# endif
+    const char *pmlenv;
 
-    /* PERL_ARGS_ASSERT_MEM_LOG_COMMON; */
+    PERL_ARGS_ASSERT_MEM_LOG_COMMON;
 
-# ifdef PERL_MEM_LOG_ENV
-    s = PerlEnv_getenv(mlt < MLT_NEW_SV ? "PERL_MEM_LOG" : "PERL_SV_LOG");
-    if (s ? atoi(s) : 0)
-# endif
+    pmlenv = PerlEnv_getenv("PERL_MEM_LOG");
+    if (!pmlenv)
+	return;
+    if (mlt < MLT_NEW_SV ? strchr(pmlenv,'m') : strchr(pmlenv,'s'))
     {
 	/* We can't use SVs or PerlIO for obvious reasons,
 	 * so we'll use stdio and low-level IO instead. */
 	char buf[PERL_MEM_LOG_SPRINTF_BUF_SIZE];
-# ifdef PERL_MEM_LOG_TIMESTAMP
+
 #   ifdef HAS_GETTIMEOFDAY
 #     define MEM_LOG_TIME_FMT	"%10d.%06d: "
 #     define MEM_LOG_TIME_ARG	(int)tv.tv_sec, (int)tv.tv_usec
@@ -5551,24 +5544,17 @@ S_mem_log_common(enum mem_log_type mlt, const UV n,
 	 * gettimeofday() (see ext/Time-HiRes), the easiest way is
 	 * probably that they would be used to fill in the struct
 	 * timeval. */
-# endif
 	{
-	    int fd = PERL_MEM_LOG_FD;
 	    STRLEN len;
+	    int fd = atoi(pmlenv);
+	    if (!fd)
+		fd = PERL_MEM_LOG_FD;
 
-# ifdef PERL_MEM_LOG_ENV_FD
-	    if ((s = PerlEnv_getenv("PERL_MEM_LOG_FD"))) {
-		fd = atoi(s);
-	    }
-# endif
-# ifdef PERL_MEM_LOG_TIMESTAMP
-	    s = PerlEnv_getenv("PERL_MEM_LOG_TIMESTAMP");
-	    if (!s || atoi(s)) {
+	    if (strchr(pmlenv, 't')) {
 		len = my_snprintf(buf, sizeof(buf),
 				MEM_LOG_TIME_FMT, MEM_LOG_TIME_ARG);
 		PerlLIO_write(fd, buf, len);
 	    }
-# endif
 	    switch (mlt) {
 	    case MLT_ALLOC:
 		len = my_snprintf(buf, sizeof(buf),