diff --git a/Makefile.in b/Makefile.in
index b1925d6b..c9f8928a 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -93,7 +93,8 @@ NASM =	asm/nasm.$(O)
 NDISASM = disasm/ndisasm.$(O)
 
 LIBOBJ = stdlib/snprintf.$(O) stdlib/vsnprintf.$(O) stdlib/strlcpy.$(O) \
-	stdlib/strnlen.$(O) \
+	stdlib/strnlen.$(O) stdlib/strrchrnul.$(O) \
+	\
 	nasmlib/ver.$(O) \
 	nasmlib/crc64.$(O) nasmlib/malloc.$(O) \
 	nasmlib/md5c.$(O) nasmlib/string.$(O) \
@@ -105,7 +106,9 @@ LIBOBJ = stdlib/snprintf.$(O) stdlib/vsnprintf.$(O) stdlib/strlcpy.$(O) \
 	nasmlib/raa.$(O) nasmlib/saa.$(O) \
 	nasmlib/strlist.$(O) \
 	nasmlib/perfhash.$(O) nasmlib/badenum.$(O) \
+	\
 	common/common.$(O) \
+	\
 	x86/insnsa.$(O) x86/insnsb.$(O) x86/insnsd.$(O) x86/insnsn.$(O) \
 	x86/regs.$(O) x86/regvals.$(O) x86/regflags.$(O) x86/regdis.$(O) \
 	x86/disp8.$(O) x86/iflag.$(O) \
diff --git a/Mkfiles/msvc.mak b/Mkfiles/msvc.mak
index 425faa95..430fa2d3 100644
--- a/Mkfiles/msvc.mak
+++ b/Mkfiles/msvc.mak
@@ -69,7 +69,8 @@ NASM =	asm\nasm.$(O)
 NDISASM = disasm\ndisasm.$(O)
 
 LIBOBJ = stdlib\snprintf.$(O) stdlib\vsnprintf.$(O) stdlib\strlcpy.$(O) \
-	stdlib\strnlen.$(O) \
+	stdlib\strnlen.$(O) stdlib\strrchrnul.$(O) \
+	\
 	nasmlib\ver.$(O) \
 	nasmlib\crc64.$(O) nasmlib\malloc.$(O) \
 	nasmlib\md5c.$(O) nasmlib\string.$(O) \
@@ -81,7 +82,9 @@ LIBOBJ = stdlib\snprintf.$(O) stdlib\vsnprintf.$(O) stdlib\strlcpy.$(O) \
 	nasmlib\raa.$(O) nasmlib\saa.$(O) \
 	nasmlib\strlist.$(O) \
 	nasmlib\perfhash.$(O) nasmlib\badenum.$(O) \
+	\
 	common\common.$(O) \
+	\
 	x86\insnsa.$(O) x86\insnsb.$(O) x86\insnsd.$(O) x86\insnsn.$(O) \
 	x86\regs.$(O) x86\regvals.$(O) x86\regflags.$(O) x86\regdis.$(O) \
 	x86\disp8.$(O) x86\iflag.$(O) \
diff --git a/Mkfiles/openwcom.mak b/Mkfiles/openwcom.mak
index 8ac1ebcb..9acb50a9 100644
--- a/Mkfiles/openwcom.mak
+++ b/Mkfiles/openwcom.mak
@@ -54,7 +54,8 @@ NASM =	asm/nasm.$(O)
 NDISASM = disasm/ndisasm.$(O)
 
 LIBOBJ = stdlib/snprintf.$(O) stdlib/vsnprintf.$(O) stdlib/strlcpy.$(O) &
-	stdlib/strnlen.$(O) &
+	stdlib/strnlen.$(O) stdlib/strrchrnul.$(O) &
+	&
 	nasmlib/ver.$(O) &
 	nasmlib/crc64.$(O) nasmlib/malloc.$(O) &
 	nasmlib/md5c.$(O) nasmlib/string.$(O) &
@@ -66,7 +67,9 @@ LIBOBJ = stdlib/snprintf.$(O) stdlib/vsnprintf.$(O) stdlib/strlcpy.$(O) &
 	nasmlib/raa.$(O) nasmlib/saa.$(O) &
 	nasmlib/strlist.$(O) &
 	nasmlib/perfhash.$(O) nasmlib/badenum.$(O) &
+	&
 	common/common.$(O) &
+	&
 	x86/insnsa.$(O) x86/insnsb.$(O) x86/insnsd.$(O) x86/insnsn.$(O) &
 	x86/regs.$(O) x86/regvals.$(O) x86/regflags.$(O) x86/regdis.$(O) &
 	x86/disp8.$(O) x86/iflag.$(O) &
diff --git a/asm/nasm.c b/asm/nasm.c
index dc97c176..0ffb036c 100644
--- a/asm/nasm.c
+++ b/asm/nasm.c
@@ -75,7 +75,7 @@ struct forwrefinfo {            /* info held on forward refs. */
 };
 
 static void parse_cmdline(int, char **, int);
-static void assemble_file(char *, StrList **);
+static void assemble_file(const char *, StrList **);
 static bool is_suppressed_warning(int severity);
 static bool skip_this_pass(int severity);
 static void nasm_verror_gnu(int severity, const char *fmt, va_list args);
@@ -94,10 +94,11 @@ int globalbnd = 0;
 
 struct compile_time official_compile_time;
 
-static char inname[FILENAME_MAX];
-static char outname[FILENAME_MAX];
-static char listname[FILENAME_MAX];
-static char errname[FILENAME_MAX];
+const char *inname;
+const char *outname;
+static const char *listname;
+static const char *errname;
+
 static int globallineno;        /* for forward-reference tracking */
 /* static int pass = 0; */
 const struct ofmt *ofmt = &OF_DEFAULT;
@@ -383,6 +384,10 @@ int main(int argc, char **argv)
     if (ofmt->stdmac)
         preproc->extra_stdmac(ofmt->stdmac);
 
+    /* no output file name? */
+    if (!outname)
+        outname = filename_set_extension(inname, ofmt->extension);
+
     /* define some macros dependent of command-line */
     define_macros_late();
 
@@ -398,8 +403,6 @@ int main(int argc, char **argv)
                 preproc->include_path(NULL);    /* "assume generated" */
 
             preproc->reset(inname, 0, depend_ptr);
-            if (outname[0] == '\0')
-                ofmt->filename(inname, outname);
             ofile = NULL;
             while ((line = preproc->getline()))
                 nasm_free(line);
@@ -410,7 +413,7 @@ int main(int argc, char **argv)
             int32_t prior_linnum = 0;
             int lineinc = 0;
 
-            if (*outname) {
+            if (outname) {
                 ofile = nasm_open_write(outname, NF_TEXT);
                 if (!ofile)
                     nasm_fatal(ERR_NOFILE,
@@ -456,15 +459,6 @@ int main(int argc, char **argv)
     }
 
     if (operating_mode & OP_NORMAL) {
-        /*
-         * We must call ofmt->filename _anyway_, even if the user
-         * has specified their own output file, because some
-         * formats (eg OBJ and COFF) use ofmt->filename to find out
-         * the name of the input file and then put that inside the
-         * file.
-         */
-        ofmt->filename(inname, outname);
-
         ofile = nasm_open_write(outname, (ofmt->flags & OFMT_TEXT) ? NF_TEXT : NF_BINARY);
         if (!ofile)
             nasm_fatal(ERR_NOFILE,
@@ -537,15 +531,12 @@ static char *get_param(char *p, char *q, bool *advance)
 /*
  * Copy a filename
  */
-static void copy_filename(char *dst, const char *src)
+static void copy_filename(const char **dst, const char *src, const char *what)
 {
-    size_t len = strlen(src);
+    if (*dst)
+        nasm_fatal(0, "more than one %s file specified: %s\n", what, src);
 
-    if (len >= (size_t)FILENAME_MAX) {
-        nasm_fatal(ERR_NOFILE, "file name too long");
-        return;
-    }
-    strncpy(dst, src, FILENAME_MAX);
+    *dst = nasm_strdup(src);
 }
 
 /*
@@ -746,7 +737,7 @@ static bool process_arg(char *p, char *q, int pass)
 
         case 'o':       /* output file */
             if (pass == 2)
-                copy_filename(outname, param);
+                copy_filename(&outname, param, "output");
             break;
 
         case 'f':       /* output format */
@@ -832,12 +823,12 @@ static bool process_arg(char *p, char *q, int pass)
 
         case 'l':       /* listing file */
             if (pass == 2)
-                copy_filename(listname, param);
+                copy_filename(&listname, param, "listing");
             break;
 
         case 'Z':       /* error messages file */
             if (pass == 1)
-                copy_filename(errname, param);
+                copy_filename(&errname, param, "error");
             break;
 
         case 'F':       /* specify debug format */
@@ -1096,12 +1087,8 @@ static bool process_arg(char *p, char *q, int pass)
             break;
         }
     } else if (pass == 2) {
-        if (*inname) {
-            nasm_error(ERR_NONFATAL | ERR_NOFILE | ERR_USAGE,
-                         "more than one input file specified");
-        } else {
-            copy_filename(inname, p);
-        }
+        /* In theory we could allow multiple input files... */
+        copy_filename(&inname, p, "input");
     }
 
     return advance;
@@ -1215,8 +1202,6 @@ static void parse_cmdline(int argc, char **argv, int pass)
     char *envreal, *envcopy = NULL, *p;
     int i;
 
-    *inname = *outname = *listname = *errname = '\0';
-
     /* Initialize all the warnings to their default state */
     for (i = 0; i < ERR_WARN_ALL; i++) {
         warning_state_init[i] = warning_state[i] =
@@ -1274,18 +1259,16 @@ static void parse_cmdline(int argc, char **argv, int pass)
     if (pass != 2)
         return;
 
-    if (!*inname)
-        nasm_error(ERR_NONFATAL | ERR_NOFILE | ERR_USAGE,
-                   "no input file specified");
-    else if (!strcmp(inname, errname)   ||
-             !strcmp(inname, outname)   ||
-             !strcmp(inname, listname)  ||
-             (depend_file && !strcmp(inname, depend_file)))
-        nasm_fatal(ERR_NOFILE | ERR_USAGE,
-                   "file `%s' is both input and output file",
-                   inname);
+    if (!inname)
+        nasm_fatal(ERR_NOFILE | ERR_USAGE, "no input file specified");
 
-    if (*errname) {
+    else if ((errname && !strcmp(inname, errname)) ||
+             (outname && !strcmp(inname, outname)) ||
+             (listname &&  !strcmp(inname, listname))  ||
+             (depend_file && !strcmp(inname, depend_file)))
+        nasm_fatal(ERR_USAGE, "will not overwrite input file");
+
+    if (errname) {
         error_file = nasm_open_write(errname, NF_TEXT);
         if (!error_file) {
             error_file = stderr;        /* Revert to default! */
@@ -1296,7 +1279,7 @@ static void parse_cmdline(int argc, char **argv, int pass)
     }
 }
 
-static void assemble_file(char *fname, StrList **depend_ptr)
+static void assemble_file(const char *fname, StrList **depend_ptr)
 {
     char *line;
     insn output_ins;
@@ -1323,7 +1306,7 @@ static void assemble_file(char *fname, StrList **depend_ptr)
         cpu = cmd_cpu;
         if (pass0 == 2) {
 	    lfmt->init(listname);
-        } else if (passn == 1 && *listname) {
+        } else if (passn == 1 && listname) {
             /* Remove the list file in case we die before the output pass */
             remove(listname);
         }
diff --git a/asm/preproc-nop.c b/asm/preproc-nop.c
index 3d2c57cf..186e87d2 100644
--- a/asm/preproc-nop.c
+++ b/asm/preproc-nop.c
@@ -63,7 +63,7 @@ static void nop_init(void)
     /* Nothing to do */
 }
 
-static void nop_reset(char *file, int pass, StrList **deplist)
+static void nop_reset(const char *file, int pass, StrList **deplist)
 {
     src_set(0, file);
     nop_lineinc = 1;
diff --git a/asm/preproc.c b/asm/preproc.c
index 475926d8..744747fd 100644
--- a/asm/preproc.c
+++ b/asm/preproc.c
@@ -4970,7 +4970,7 @@ static void pp_verror(int severity, const char *fmt, va_list arg)
 }
 
 static void
-pp_reset(char *file, int apass, StrList **deplist)
+pp_reset(const char *file, int apass, StrList **deplist)
 {
     Token *t;
 
diff --git a/configure.ac b/configure.ac
index 071b043c..1f492103 100644
--- a/configure.ac
+++ b/configure.ac
@@ -115,6 +115,7 @@ AC_CHECK_FUNCS(strcasecmp stricmp)
 AC_CHECK_FUNCS(strncasecmp strnicmp)
 AC_CHECK_FUNCS(strsep)
 AC_CHECK_FUNCS(strnlen)
+AC_CHECK_FUNCS(strrchrnul)
 
 AC_CHECK_FUNCS(getuid)
 AC_CHECK_FUNCS(getgid)
@@ -146,10 +147,11 @@ PA_HAVE_FUNC(__builtin_clzll, (0ULL))
 PA_HAVE_FUNC(_BitScanReverse, (0))
 PA_HAVE_FUNC(_BitScanReverse64, (0))
 
-dnl Functions for which we have replacements available in lib/
+dnl Functions for which we have replacements available in stdlib/
 AC_CHECK_FUNCS([vsnprintf _vsnprintf])
 AC_CHECK_FUNCS([snprintf _snprintf])
 AC_CHECK_FUNCS([strlcpy])
+AC_CHECK_FUNCS([strrchrnul])
 
 dnl These types are POSIX-specific, and Windows does it differently...
 AC_CHECK_TYPES([struct _stati64])
@@ -167,6 +169,7 @@ AC_CHECK_DECLS(strnicmp)
 AC_CHECK_DECLS(strsep)
 AC_CHECK_DECLS(strlcpy)
 AC_CHECK_DECLS(strnlen)
+AC_CHECK_DECLS(strrchrnul)
 
 dnl Check for missing types
 AC_TYPE_UINTPTR_T
diff --git a/include/compiler.h b/include/compiler.h
index db4c7e62..6e919d3d 100644
--- a/include/compiler.h
+++ b/include/compiler.h
@@ -155,6 +155,10 @@ int vsnprintf(char *, size_t, const char *, va_list);
 size_t strlcpy(char *, const char *, size_t);
 #endif
 
+#if !defined(HAVE_STRCHRNUL) || !HAVE_DECL_STRCHRNUL
+char *strrchrnul(const char *, int);
+#endif
+
 #ifndef __cplusplus		/* C++ has false, true, bool as keywords */
 # ifdef HAVE_STDBOOL_H
 #  include <stdbool.h>
diff --git a/include/nasm.h b/include/nasm.h
index f640cd63..48590f20 100644
--- a/include/nasm.h
+++ b/include/nasm.h
@@ -64,10 +64,6 @@ extern struct compile_time official_compile_time;
 #define NO_SEG -1L              /* null segment value */
 #define SEG_ABS 0x40000000L     /* mask for far-absolute segments */
 
-#ifndef FILENAME_MAX
-#define FILENAME_MAX 256
-#endif
-
 #ifndef PREFIX_MAX
 #define PREFIX_MAX 10
 #endif
@@ -354,7 +350,7 @@ struct preproc_ops {
      * of the pass, an error reporting function, an evaluator
      * function, and a listing generator to talk to.
      */
-    void (*reset)(char *file, int pass, StrList **deplist);
+    void (*reset)(const char *file, int pass, StrList **deplist);
 
     /*
      * Called to fetch a line of preprocessed source. The line
@@ -782,6 +778,11 @@ struct ofmt {
      */
     const char *shortname;
 
+    /*
+     * Default output filename extension, or a null string
+     */
+    const char *extension;
+
     /*
      * Output format flags.
      */
@@ -928,25 +929,6 @@ struct ofmt {
     enum directive_result
     (*directive)(enum directive directive, char *value, int pass);
 
-    /*
-     * This procedure is called before anything else - even before
-     * the "init" routine - and is passed the name of the input
-     * file from which this output file is being generated. It
-     * should return its preferred name for the output file in
-     * `outname', if outname[0] is not '\0', and do nothing to
-     * `outname' otherwise. Since it is called before the driver is
-     * properly initialized, it has to be passed its error handler
-     * separately.
-     *
-     * This procedure may also take its own copy of the input file
-     * name for use in writing the output file: it is _guaranteed_
-     * that it will be called before the "init" routine.
-     *
-     * The parameter `outname' points to an area of storage
-     * guaranteed to be at least FILENAME_MAX in size.
-     */
-    void (*filename)(char *inname, char *outname);
-
     /*
      * This procedure is called after assembly finishes, to allow
      * the output driver to clean itself up and free its memory.
@@ -1244,4 +1226,7 @@ extern int globalbits;          /* 16, 32 or 64-bit mode */
 extern int globalrel;           /* default to relative addressing? */
 extern int globalbnd;           /* default to using bnd prefix? */
 
+extern const char *inname;	/* primary input filename */
+extern const char *outname;     /* output filename */
+
 #endif
diff --git a/include/nasmlib.h b/include/nasmlib.h
index 8ea17503..78bb1e48 100644
--- a/include/nasmlib.h
+++ b/include/nasmlib.h
@@ -196,10 +196,9 @@ void pure_func seg_init(void);
 int32_t pure_func seg_alloc(void);
 
 /*
- * many output formats will be able to make use of this: a standard
- * function to add an extension to the name of the input file
+ * Add/replace or remove an extension to the end of a filename
  */
-void standard_extension(char *inname, char *outname, char *extension);
+const char *filename_set_extension(const char *inname, const char *extension);
 
 /*
  * Utility macros...
diff --git a/nasmlib/filename.c b/nasmlib/filename.c
index 799eb89a..172ae0bc 100644
--- a/nasmlib/filename.c
+++ b/nasmlib/filename.c
@@ -1,6 +1,6 @@
 /* ----------------------------------------------------------------------- *
- *   
- *   Copyright 1996-2016 The NASM Authors - All Rights Reserved
+ *
+ *   Copyright 1996-2017 The NASM Authors - All Rights Reserved
  *   See the file AUTHORS included with the NASM distribution for
  *   the specific copyright holders.
  *
@@ -14,7 +14,7 @@
  *     copyright notice, this list of conditions and the following
  *     disclaimer in the documentation and/or other materials provided
  *     with the distribution.
- *     
+ *
  *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
@@ -39,31 +39,25 @@
 #include "nasmlib.h"
 #include "error.h"
 
-void standard_extension(char *inname, char *outname, char *extension)
+/*
+ * Add/modify a filename extension, assumed to be a period-delimited
+ * field at the very end of the filename.  Returns a newly allocated
+ * string buffer.
+ */
+const char *filename_set_extension(const char *inname, const char *extension)
 {
-    char *p, *q;
+    const char *q = inname;
+    char *p;
+    size_t elen = strlen(extension);
+    size_t baselen;
 
-    if (*outname)               /* file name already exists, */
-        return;                 /* so do nothing */
-    q = inname;
-    p = outname;
-    while (*q)
-        *p++ = *q++;            /* copy, and find end of string */
-    *p = '\0';                  /* terminate it */
-    while (p > outname && *--p != '.') ;        /* find final period (or whatever) */
-    if (*p != '.')
-        while (*p)
-            p++;                /* go back to end if none found */
-    if (!strcmp(p, extension)) {        /* is the extension already there? */
-        if (*extension)
-            nasm_error(ERR_WARNING | ERR_NOFILE,
-		       "file name already ends in `%s': "
-		       "output will be in `nasm.out'", extension);
-        else
-            nasm_error(ERR_WARNING | ERR_NOFILE,
-		       "file name already has no extension: "
-		       "output will be in `nasm.out'");
-        strcpy(outname, "nasm.out");
-    } else
-        strcpy(p, extension);
+    q = strrchrnul(inname, '.');   /* find extension or end of string */
+    baselen = q - inname;
+
+    p = nasm_malloc(baselen + elen + 1);
+
+    memcpy(p, inname, baselen);
+    memcpy(p+baselen, extension, elen+1);
+
+    return p;
 }
diff --git a/output/codeview.c b/output/codeview.c
index c60d4920..c8a90e91 100644
--- a/output/codeview.c
+++ b/output/codeview.c
@@ -314,7 +314,7 @@ static void cv8_cleanup(void)
     struct coff_Section *symbol_sect = coff_sects[cv8_state.symbol_sect];
     struct coff_Section *type_sect = coff_sects[cv8_state.type_sect];
 
-    cv8_state.outfile.name = nasm_realpath(coff_outfile);
+    cv8_state.outfile.name = nasm_realpath(outname);
     cv8_state.outfile.namebytes = strlen(cv8_state.outfile.name) + 1;
 
     build_symbol_table(symbol_sect);
diff --git a/output/outaout.c b/output/outaout.c
index 83859d97..5dab46c0 100644
--- a/output/outaout.c
+++ b/output/outaout.c
@@ -894,11 +894,6 @@ static int32_t aout_segbase(int32_t segment)
     return segment;
 }
 
-static void aout_filename(char *inname, char *outname)
-{
-    standard_extension(inname, outname, ".o");
-}
-
 extern macros_t aout_stdmac[];
 
 #endif                          /* OF_AOUT || OF_AOUTB */
@@ -908,6 +903,7 @@ extern macros_t aout_stdmac[];
 const struct ofmt of_aout = {
     "Linux a.out object files",
     "aout",
+    ".o",
     0,
     32,
     null_debug_arr,
@@ -921,7 +917,6 @@ const struct ofmt of_aout = {
     null_sectalign,
     aout_segbase,
     null_directive,
-    aout_filename,
     aout_cleanup,
     NULL                        /* pragma list */
 };
@@ -933,6 +928,7 @@ const struct ofmt of_aout = {
 const struct ofmt of_aoutb = {
     "NetBSD/FreeBSD a.out object files",
     "aoutb",
+    ".o",
     0,
     32,
     null_debug_arr,
@@ -946,7 +942,6 @@ const struct ofmt of_aoutb = {
     null_sectalign,
     aout_segbase,
     null_directive,
-    aout_filename,
     aout_cleanup,
     NULL                        /* pragma list */
 };
diff --git a/output/outas86.c b/output/outas86.c
index 59b10e71..18781950 100644
--- a/output/outas86.c
+++ b/output/outas86.c
@@ -1,6 +1,6 @@
 /* ----------------------------------------------------------------------- *
  *   
- *   Copyright 1996-2013 The NASM Authors - All Rights Reserved
+ *   Copyright 1996-2017 The NASM Authors - All Rights Reserved
  *   See the file AUTHORS included with the NASM distribution for
  *   the specific copyright holders.
  *
@@ -91,8 +91,6 @@ struct Section {
     struct Piece *head, *last, **tail;
 };
 
-static char as86_module[FILENAME_MAX];
-
 static struct Section stext, sdata;
 static uint32_t bsslen;
 static int32_t bssindex;
@@ -103,13 +101,13 @@ static uint32_t nsyms;
 static struct RAA *bsym;
 
 static struct SAA *strs;
-static uint32_t strslen;
+static size_t strslen;
 
 static int as86_reloc_size;
 
 static void as86_write(void);
 static void as86_write_section(struct Section *, int);
-static int as86_add_string(char *name);
+static size_t as86_add_string(const char *name);
 static void as86_sect_write(struct Section *, const uint8_t *,
                             uint32_t);
 
@@ -135,7 +133,8 @@ static void as86_init(void)
     strs = saa_init(1L);
     strslen = 0;
 
-    as86_add_string(as86_module);
+    /* as86 module name = input file minus extension */
+    as86_add_string(filename_set_extension(inname, ""));
 }
 
 static void as86_cleanup(void)
@@ -183,12 +182,12 @@ static int32_t as86_section_names(char *name, int pass, int *bits)
         return NO_SEG;
 }
 
-static int as86_add_string(char *name)
+static size_t as86_add_string(const char *name)
 {
-    int pos = strslen;
-    int length = strlen(name);
+    size_t pos = strslen;
+    size_t length = strlen(name);
 
-    saa_wbytes(strs, name, (int32_t)(length + 1));
+    saa_wbytes(strs, name, length + 1);
     strslen += 1 + length;
 
     return pos;
@@ -611,24 +610,12 @@ static int32_t as86_segbase(int32_t segment)
     return segment;
 }
 
-static void as86_filename(char *inname, char *outname)
-{
-    char *p;
-
-    if ((p = strrchr(inname, '.')) != NULL) {
-        strncpy(as86_module, inname, p - inname);
-        as86_module[p - inname] = '\0';
-    } else
-        strcpy(as86_module, inname);
-
-    standard_extension(inname, outname, ".o");
-}
-
 extern macros_t as86_stdmac[];
 
 const struct ofmt of_as86 = {
     "Linux as86 (bin86 version 0.3) object files",
     "as86",
+    ".o",
     0,
     32,
     null_debug_arr,
@@ -642,7 +629,6 @@ const struct ofmt of_as86 = {
     null_sectalign,
     as86_segbase,
     null_directive,
-    as86_filename,
     as86_cleanup,
     NULL                        /* pragma list */
 };
diff --git a/output/outbin.c b/output/outbin.c
index 7f694c4f..e28b809e 100644
--- a/output/outbin.c
+++ b/output/outbin.c
@@ -1,6 +1,6 @@
 /* ----------------------------------------------------------------------- *
  *   
- *   Copyright 1996-2013 The NASM Authors - All Rights Reserved
+ *   Copyright 1996-2017 The NASM Authors - All Rights Reserved
  *   See the file AUTHORS included with the NASM distribution for
  *   the specific copyright holders.
  *
@@ -161,7 +161,6 @@ static int origin_defined;
 #define MAP_SECTIONS     4
 #define MAP_SYMBOLS      8
 static int map_control = 0;
-static char *infile, *outfile;
 
 extern macros_t bin_stdmac[];
 
@@ -580,7 +579,7 @@ static void bin_cleanup(void)
         for (h = 63; h; h--)
             fputc('-', rf);
         fprintf(rf, "\n\nSource file:  %s\nOutput file:  %s\n\n",
-                infile, outfile);
+                inname, outname);
 
         if (map_control & MAP_ORIGIN) { /* Display program origin. */
             fprintf(rf, "-- Program origin ");
@@ -1371,27 +1370,6 @@ bin_directive(enum directive directive, char *args, int pass)
     }
 }
 
-static void bin_filename(char *inname, char *outname)
-{
-    standard_extension(inname, outname, "");
-    infile = inname;
-    outfile = outname;
-}
-
-static void ith_filename(char *inname, char *outname)
-{
-    standard_extension(inname, outname, ".ith");
-    infile = inname;
-    outfile = outname;
-}
-
-static void srec_filename(char *inname, char *outname)
-{
-    standard_extension(inname, outname, ".srec");
-    infile = inname;
-    outfile = outname;
-}
-
 static int32_t bin_segbase(int32_t segment)
 {
     return segment;
@@ -1650,6 +1628,7 @@ static void do_output_srec(void)
 const struct ofmt of_bin = {
     "flat-form binary files (e.g. DOS .COM, .SYS)",
     "bin",
+    "",
     0,
     64,
     null_debug_arr,
@@ -1663,7 +1642,6 @@ const struct ofmt of_bin = {
     bin_sectalign,
     bin_segbase,
     bin_directive,
-    bin_filename,
     bin_cleanup,
     NULL                        /* pragma list */
 };
@@ -1671,6 +1649,7 @@ const struct ofmt of_bin = {
 const struct ofmt of_ith = {
     "Intel hex",
     "ith",
+    ".ith",                     /* really should have been ".hex"... */
     OFMT_TEXT,
     64,
     null_debug_arr,
@@ -1684,7 +1663,6 @@ const struct ofmt of_ith = {
     bin_sectalign,
     bin_segbase,
     bin_directive,
-    ith_filename,
     bin_cleanup,
     NULL                        /* pragma list */
 };
@@ -1692,6 +1670,7 @@ const struct ofmt of_ith = {
 const struct ofmt of_srec = {
     "Motorola S-records",
     "srec",
+    ".srec",
     OFMT_TEXT,
     64,
     null_debug_arr,
@@ -1705,7 +1684,6 @@ const struct ofmt of_srec = {
     bin_sectalign,
     bin_segbase,
     bin_directive,
-    srec_filename,
     bin_cleanup,
     NULL                        /* pragma list */
 };
diff --git a/output/outcoff.c b/output/outcoff.c
index d3a1b22c..54aed727 100644
--- a/output/outcoff.c
+++ b/output/outcoff.c
@@ -1,6 +1,6 @@
 /* ----------------------------------------------------------------------- *
  *
- *   Copyright 1996-2014 The NASM Authors - All Rights Reserved
+ *   Copyright 1996-2017 The NASM Authors - All Rights Reserved
  *   See the file AUTHORS included with the NASM distribution for
  *   the specific copyright holders.
  *
@@ -106,9 +106,6 @@ bool win32, win64;
 static int32_t imagebase_sect;
 #define WRT_IMAGEBASE "..imagebase"
 
-char coff_infile[FILENAME_MAX];
-char coff_outfile[FILENAME_MAX];
-
 /*
  * Some common section flags by default
  */
@@ -1080,7 +1077,7 @@ static void coff_write_symbols(void)
      * The `.file' record, and the file name auxiliary record.
      */
     coff_symbol(".file", 0L, 0L, -2, 0, 0x67, 1);
-    strncpy(filename, coff_infile, 18);
+    strncpy(filename, inname, 18);
     nasm_write(filename, 18, ofile);
 
     /*
@@ -1143,20 +1140,6 @@ static int32_t coff_segbase(int32_t segment)
     return segment;
 }
 
-static void coff_std_filename(char *inname, char *outname)
-{
-    strcpy(coff_infile, inname);
-    standard_extension(inname, outname, ".o");
-    strcpy(coff_outfile, outname);
-}
-
-static void coff_win32_filename(char *inname, char *outname)
-{
-    strcpy(coff_infile, inname);
-    standard_extension(inname, outname, ".obj");
-    strcpy(coff_outfile, outname);
-}
-
 extern macros_t coff_stdmac[];
 
 #endif /* defined(OF_COFF) || defined(OF_WIN32) */
@@ -1166,6 +1149,7 @@ extern macros_t coff_stdmac[];
 const struct ofmt of_coff = {
     "COFF (i386) object files (e.g. DJGPP for DOS)",
     "coff",
+    ".o",
     0,
     32,
     null_debug_arr,
@@ -1179,7 +1163,6 @@ const struct ofmt of_coff = {
     coff_sectalign,
     coff_segbase,
     coff_directives,
-    coff_std_filename,
     coff_cleanup,
     NULL                        /* pragma list */
 };
@@ -1195,6 +1178,7 @@ static const struct dfmt * const win32_debug_arr[2] = { &df_cv8, NULL };
 const struct ofmt of_win32 = {
     "Microsoft Win32 (i386) object files",
     "win32",
+    ".obj",
     0,
     32,
     win32_debug_arr,
@@ -1208,7 +1192,6 @@ const struct ofmt of_win32 = {
     coff_sectalign,
     coff_segbase,
     coff_directives,
-    coff_win32_filename,
     coff_cleanup,
     NULL                        /* pragma list */
 };
@@ -1222,6 +1205,7 @@ static const struct dfmt * const win64_debug_arr[2] = { &df_cv8, NULL };
 const struct ofmt of_win64 = {
     "Microsoft Win64 (x86-64) object files",
     "win64",
+    ".obj",
     0,
     64,
     win64_debug_arr,
@@ -1235,7 +1219,6 @@ const struct ofmt of_win64 = {
     coff_sectalign,
     coff_segbase,
     coff_directives,
-    coff_win32_filename,
     coff_cleanup,
     NULL                        /* pragma list */
 };
diff --git a/output/outdbg.c b/output/outdbg.c
index b7b6ef04..c57e0af0 100644
--- a/output/outdbg.c
+++ b/output/outdbg.c
@@ -66,6 +66,8 @@ static void dbg_init(void)
 {
     dbgsect = NULL;
     fprintf(ofile, "NASM Output format debug dump\n");
+    fprintf(ofile, "input file  = %s\n", inname);
+    fprintf(ofile, "output file = %s\n", outname);
 }
 
 static void dbg_cleanup(void)
@@ -369,11 +371,6 @@ dbg_pragma(const struct pragma *pragma)
     return DIRR_OK;
 }
 
-static void dbg_filename(char *inname, char *outname)
-{
-    standard_extension(inname, outname, ".dbg");
-}
-
 static const char * const types[] = {
     "unknown", "label", "byte", "word", "dword", "float", "qword", "tbyte"
 };
@@ -443,6 +440,7 @@ extern macros_t dbg_stdmac[];
 const struct ofmt of_dbg = {
     "Trace of all info passed to output stage",
     "dbg",
+    ".dbg",
     OFMT_TEXT,
     64,
     debug_debug_arr,
@@ -456,7 +454,6 @@ const struct ofmt of_dbg = {
     dbg_sectalign,
     dbg_segbase,
     dbg_directive,
-    dbg_filename,
     dbg_cleanup,
     dbg_pragma_list
 };
diff --git a/output/outelf.c b/output/outelf.c
index 6d0ce56f..c0b37e46 100644
--- a/output/outelf.c
+++ b/output/outelf.c
@@ -2224,12 +2224,6 @@ static int32_t elf_segbase(int32_t segment)
     return segment;
 }
 
-static void elf_filename(char *inname, char *outname)
-{
-    strcpy(elf_module, inname);
-    standard_extension(inname, outname, ".o");
-}
-
 extern macros_t elf_stdmac[];
 
 /* Claim "elf" as a pragma namespace, for the future */
@@ -2272,6 +2266,7 @@ static const struct dfmt * const elf32_debugs_arr[3] =
 const struct ofmt of_elf32 = {
     "ELF32 (i386) object files (e.g. Linux)",
     "elf32",
+    ".o",
     0,
     32,
     elf32_debugs_arr,
@@ -2285,7 +2280,6 @@ const struct ofmt of_elf32 = {
     elf_sectalign,
     elf_segbase,
     elf_directive,
-    elf_filename,
     elf_cleanup,
     elf_pragma_list,
 };
@@ -2322,6 +2316,7 @@ static const struct dfmt * const elf64_debugs_arr[3] =
 const struct ofmt of_elf64 = {
     "ELF64 (x86_64) object files (e.g. Linux)",
     "elf64",
+    ".o",
     0,
     64,
     elf64_debugs_arr,
@@ -2335,7 +2330,6 @@ const struct ofmt of_elf64 = {
     elf_sectalign,
     elf_segbase,
     elf_directive,
-    elf_filename,
     elf_cleanup,
     elf_pragma_list,
 };
@@ -2372,6 +2366,7 @@ static const struct dfmt * const elfx32_debugs_arr[3] =
 const struct ofmt of_elfx32 = {
     "ELFX32 (x86_64) object files (e.g. Linux)",
     "elfx32",
+    ".o",
     0,
     64,
     elfx32_debugs_arr,
@@ -2385,7 +2380,6 @@ const struct ofmt of_elfx32 = {
     elf_sectalign,
     elf_segbase,
     elf_directive,
-    elf_filename,
     elf_cleanup,
     NULL                        /* pragma list */
 };
diff --git a/output/outieee.c b/output/outieee.c
index e96c723b..114c8151 100644
--- a/output/outieee.c
+++ b/output/outieee.c
@@ -886,15 +886,6 @@ static int32_t ieee_segbase(int32_t segment)
     return segment;             /* no special treatment */
 }
 
-/*
- * filename
- */
-static void ieee_filename(char *inname, char *outname)
-{
-    strcpy(ieee_infile, inname);
-    standard_extension(inname, outname, ".o");
-}
-
 static void ieee_write_file(void)
 {
     const struct tm * const thetime = &official_compile_time.local;
@@ -1507,6 +1498,7 @@ static const struct dfmt * const ladsoft_debug_arr[3] = {
 const struct ofmt of_ieee = {
     "IEEE-695 (LADsoft variant) object file format",
     "ieee",
+    ".o",
     OFMT_TEXT,
     32,
     ladsoft_debug_arr,
@@ -1520,7 +1512,6 @@ const struct ofmt of_ieee = {
     ieee_sectalign,
     ieee_segbase,
     ieee_directive,
-    ieee_filename,
     ieee_cleanup,
     NULL                        /* pragma list */
 };
diff --git a/output/outmacho.c b/output/outmacho.c
index 4aefe3f3..742c2948 100644
--- a/output/outmacho.c
+++ b/output/outmacho.c
@@ -1106,12 +1106,6 @@ static int32_t macho_segbase(int32_t section)
     return section;
 }
 
-static void macho_filename(char *inname, char *outname)
-{
-    standard_extension(inname, outname, ".o");
-    module_name = inname;
-}
-
 extern macros_t macho_stdmac[];
 
 /* Comparison function for qsort symbol layout.  */
@@ -2293,6 +2287,7 @@ static const struct dfmt * const macho32_df_arr[2] =
 const struct ofmt of_macho32 = {
     "NeXTstep/OpenStep/Rhapsody/Darwin/MacOS X (i386) object files",
     "macho32",
+    ".o",
     0,
     32,
     macho32_df_arr,
@@ -2306,7 +2301,6 @@ const struct ofmt of_macho32 = {
     macho_sectalign,
     macho_segbase,
     null_directive,
-    macho_filename,
     macho_cleanup,
     macho_pragma_list
 };
@@ -2358,6 +2352,7 @@ static const struct dfmt * const macho64_df_arr[2] =
 const struct ofmt of_macho64 = {
     "NeXTstep/OpenStep/Rhapsody/Darwin/MacOS X (x86_64) object files",
     "macho64",
+    ".o",
     0,
     64,
     macho64_df_arr,
@@ -2371,7 +2366,6 @@ const struct ofmt of_macho64 = {
     macho_sectalign,
     macho_segbase,
     null_directive,
-    macho_filename,
     macho_cleanup,
     macho_pragma_list,
 };
diff --git a/output/outobj.c b/output/outobj.c
index db514431..c9418db0 100644
--- a/output/outobj.c
+++ b/output/outobj.c
@@ -1940,12 +1940,6 @@ static int32_t obj_segbase(int32_t segment)
     return segment;             /* no special treatment */
 }
 
-static void obj_filename(char *inname, char *outname)
-{
-    strcpy(obj_infile, inname);
-    standard_extension(inname, outname, ".obj");
-}
-
 /* Get a file timestamp in MS-DOS format */
 static uint32_t obj_file_timestamp(const char *pathname)
 {
@@ -2705,6 +2699,7 @@ static const struct pragma_facility obj_pragma_list[] = {
 const struct ofmt of_obj = {
     "MS-DOS 16-bit/32-bit OMF object files",
     "obj",
+    ".obj",
     0,
     32,
     borland_debug_arr,
@@ -2718,7 +2713,6 @@ const struct ofmt of_obj = {
     obj_sectalign,
     obj_segbase,
     obj_directive,
-    obj_filename,
     obj_cleanup,
     obj_pragma_list
 };
diff --git a/output/outrdf2.c b/output/outrdf2.c
index ebc6a1f2..3a218a44 100644
--- a/output/outrdf2.c
+++ b/output/outrdf2.c
@@ -760,16 +760,12 @@ rdf2_directive(enum directive directive, char *value, int pass)
     }
 }
 
-static void rdf2_filename(char *inname, char *outname)
-{
-    standard_extension(inname, outname, ".rdf");
-}
-
 extern macros_t rdf2_stdmac[];
 
 const struct ofmt of_rdf2 = {
     "Relocatable Dynamic Object File Format v2.0",
     "rdf",
+    ".rdf",
     0,
     64,
     null_debug_arr,
@@ -783,7 +779,6 @@ const struct ofmt of_rdf2 = {
     null_sectalign,
     rdf2_segbase,
     rdf2_directive,
-    rdf2_filename,
     rdf2_cleanup,
     NULL                        /* pragma list */
 };
diff --git a/stdlib/strrchrnul.c b/stdlib/strrchrnul.c
new file mode 100644
index 00000000..d25148eb
--- /dev/null
+++ b/stdlib/strrchrnul.c
@@ -0,0 +1,50 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2017 The NASM Authors - All Rights Reserved
+ *   See the file AUTHORS included with the NASM distribution for
+ *   the specific copyright holders.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following
+ *   conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above
+ *     copyright notice, this list of conditions and the following
+ *     disclaimer in the documentation and/or other materials provided
+ *     with the distribution.
+ *
+ *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ *     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ *     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ *     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ *     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ *     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ *     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ *     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * ----------------------------------------------------------------------- */
+
+#include "compiler.h"
+#include <string.h>
+
+#ifndef HAVE_STRRCHRNUL
+
+char *strrchrnul(const char *s, int c)
+{
+    char *p;
+
+    p = strrchr(s, c);
+    if (!p)
+        p = strchr(s, '\0');
+
+    return p;
+}
+
+#endif