From: Jarkko Hietaniemi <jhi@iki.fi>
Date: Mon, 26 Mar 2007 19:50:11 +0000 (-0400)
Subject: util.c [PATCH] perlhack.pod (Was: Re: threads crashes in Tru64)
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=ad7244db27635ed088fc05a8a69e99bbb19c36d6;p=p5sagit%2Fp5-mst-13.2.git

util.c [PATCH] perlhack.pod (Was: Re: threads crashes in Tru64)
Message-ID: <46085C33.1030601@iki.fi>

p4raw-id: //depot/perl@30771
---

diff --git a/pod/perlhack.pod b/pod/perlhack.pod
index 05e8751..b176b83 100644
--- a/pod/perlhack.pod
+++ b/pod/perlhack.pod
@@ -2844,6 +2844,22 @@ But in any case, try to keep the features and operating systems separate.
 
 =back
 
+=head2 Problematic System Interfaces
+
+=over 4
+
+=item *
+
+malloc(0), realloc(0), calloc(0, 0) are nonportable.  To be portable
+allocate at least one byte.  (In general you should rarely need to
+work at this low level, but instead use the various malloc wrappers.)
+
+=item *
+
+snprintf() - the return type is unportable.  Use my_snprintf() instead.
+
+=back
+
 =head2 Security problems
 
 Last but not least, here are various tips for safer coding.
diff --git a/util.c b/util.c
index 7478c39..8205aa8 100644
--- a/util.c
+++ b/util.c
@@ -258,14 +258,19 @@ Perl_safesyscalloc(MEM_SIZE count, MEM_SIZE size)
 {
     dTHX;
     Malloc_t ptr;
-#if defined(DEBUGGING) || defined(HAS_64K_LIMIT) || defined(PERL_TRACK_MEMPOOL)
-    const MEM_SIZE total_size = size * count
-#ifdef   PERL_TRACK_MEMPOOL
-	+ sTHX
-#endif
-	;
-#endif
+    MEM_SIZE total_size = 0;
 
+    /* Even though calloc() for zero bytes is strange, be robust. */
+    if (size && (count <= (MEM_SIZE)~0 / size))
+	total_size = size * count;
+    else
+	Perl_croak_nocontext(PL_memory_wrap);
+#ifdef PERL_TRACK_MEMPOOL
+    if (sTHX <= (MEM_SIZE)~0 - (MEM_SIZE)total_size)
+	total_size += sTHX;
+    else
+	Perl_croak_nocontext(PL_memory_wrap);
+#endif
 #ifdef HAS_64K_LIMIT
     if (total_size > 0xffff) {
 	PerlIO_printf(Perl_error_log,
@@ -280,11 +285,15 @@ Perl_safesyscalloc(MEM_SIZE count, MEM_SIZE size)
 #ifdef PERL_TRACK_MEMPOOL
     /* Have to use malloc() because we've added some space for our tracking
        header.  */
-    ptr = (Malloc_t)PerlMem_malloc(total_size);
+    /* malloc(0) is non-portable. */
+    ptr = (Malloc_t)PerlMem_malloc(total_size ? total_size : 1);
 #else
     /* Use calloc() because it might save a memset() if the memory is fresh
        and clean from the OS.  */
-    ptr = (Malloc_t)PerlMem_calloc(count, size);
+    if (count && size)
+	ptr = (Malloc_t)PerlMem_calloc(count, size);
+    else /* calloc(0) is non-portable. */
+	ptr = (Malloc_t)PerlMem_calloc(count ? count : 1, size ? size : 1);
 #endif
     PERL_ALLOC_CHECK(ptr);
     DEBUG_m(PerlIO_printf(Perl_debug_log, "0x%"UVxf": (%05ld) calloc %ld x %ld bytes\n",PTR2UV(ptr),(long)PL_an++,(long)count,(long)total_size));