BR 774131: date and time macros

This checkin creates the following date and time macros:

__DATE__, __TIME__, __UTC_DATE__, __UTC_TIME__: strings

__DATE_NUM__, __TIME_NUM__, __UTC_DATE_NUM__, __UTC_TIME_NUM__:
civil dates in digit-string formats

__POSIX_TIME__: time in POSIX time_t format

doc/nasmdoc.src

@@ -3111,6 +3111,56 @@ number of 16, 32 or 64. \c{__BITS__} receives the specified mode number and
 makes it globally available. This can be very useful for those who utilize
 mode-dependent macros.
 
+\S{datetime} \i\c{__DATE__} and \i\c{__TIME__}: Assembly date and time
+
+The \c{__DATE__} and \c{__TIME__} macros give the assembly date and
+time as strings, in ISO 8601 format (\c{"YYYY-MM-DD"} and \c{"HH:MM:SS"},
+respectively.)
+
+All instances of time and date macros in the same assembly session
+produce consistent output.
+
+\S{datetimenum} \i\c{__DATE_NUM__} and \i\c{__TIME_NUM__}: Numeric
+assembly date and time
+
+The \c{__DATE_NUM__} and \c{__TIME_NUM__} macros give the assembly
+date and time in numeric form; in the format \c{YYYYMMDD} and
+\c{HHMMSS} respectively.
+
+All instances of time and date macros in the same assembly session
+produce consistent output.
+
+\S{utcdatetime} \i\c{__UTC_DATE__} and \i\c{__UTC_TIME__}: Assembly UTC date and time
+
+The \c{__DATE__} and \c{__TIME__} macros give the assembly date and
+time in universal time (UTC) as strings, in ISO 8601 format
+(\c{"YYYY-MM-DD"} and \c{"HH:MM:SS"}, respectively.)  If the
+underlying platform doesn't provide UTC time, these macros are
+undefined.
+
+All instances of time and date macros in the same assembly session
+produce consistent output.
+
+\S{utcdatetimenum} \i\c{__UTC_DATE_NUM__} and \i\c{__UTC_TIME_NUM__}: Numeric
+assembly UTC date and time
+
+The \c{__UTC_DATE_NUM__} and \c{__UTC_TIME_NUM__} macros give the
+assembly date and time universal time (UTC) in numeric form; in the
+format \c{YYYYMMDD} and \c{HHMMSS} respectively.  If the
+underlying platform doesn't provide UTC time, these macros are
+undefined.
+
+All instances of time and date macros in the same assembly session
+produce consistent output.
+
+\S{posixtime} \i\c{__POSIX_TIME__}: POSIX time constant
+
+The \c{__POSIX_TIME__} macro is defined as a number containing the
+number of seconds since the POSIX epoch, 1 January 1970 00:00:00 UTC;
+excluding any leap seconds.
+
+This is computed using UTC time if available on the platform,
+otherwise it is computed using the local time as if it was UTC.
 
 \S{struc} \i\c{STRUC} and \i\c{ENDSTRUC}: \i{Declaring Structure} Data Types
 

nasm.c

@@ -15,6 +15,7 @@
 #include <ctype.h>
 #include <inttypes.h>
 #include <limits.h>
+#include <time.h>
 
 #include "nasm.h"
 #include "nasmlib.h"
@@ -53,6 +54,8 @@ int pass0, passn;
 int maxbits = 0;
 int globalrel = 0;
 
+time_t official_compile_time;
+
 static char inname[FILENAME_MAX];
 static char outname[FILENAME_MAX];
 static char listname[FILENAME_MAX];
@@ -160,8 +163,86 @@ static void nasm_fputs(const char *line, FILE * outfile)
         puts(line);
 }
 
+/* Convert a struct tm to a POSIX-style time constant */
+static int64_t posix_mktime(struct tm *tm)
+{
+    int64_t t;
+    int64_t y = tm->tm_year;
+
+    /* See IEEE 1003.1:2004, section 4.14 */
+
+    t = (y-70)*365 + (y-69)/4 - (y-1)/100 + (y+299)/400;
+    t += tm->tm_yday;
+    t *= 24;
+    t += tm->tm_hour;
+    t *= 60;
+    t += tm->tm_min;
+    t *= 60;
+    t += tm->tm_sec;
+
+    return t;
+}
+
+static void define_macros_early(void)
+{
+    char temp[128];
+    struct tm lt, *lt_p, gm, *gm_p;
+    int64_t posix_time;
+
+    lt_p = localtime(&official_compile_time);
+    if (lt_p) {
+	lt = *lt_p;
+
+	strftime(temp, sizeof temp, "__DATE__=\"%Y-%m-%d\"", &lt);
+	pp_pre_define(temp);
+	strftime(temp, sizeof temp, "__DATE_NUM__=%Y%m%d", &lt);
+	pp_pre_define(temp);
+	strftime(temp, sizeof temp, "__TIME__=\"%H:%M:%S\"", &lt);
+	pp_pre_define(temp);
+	strftime(temp, sizeof temp, "__TIME_NUM__=%H%M%S", &lt);
+	pp_pre_define(temp);
+    }
+
+    gm_p = gmtime(&official_compile_time);
+    if (gm_p) {
+	gm = *gm_p;
+
+	strftime(temp, sizeof temp, "__UTC_DATE__=\"%Y-%m-%d\"", &gm);
+	pp_pre_define(temp);
+	strftime(temp, sizeof temp, "__UTC_DATE_NUM__=%Y%m%d", &gm);
+	pp_pre_define(temp);
+	strftime(temp, sizeof temp, "__UTC_TIME__=\"%H:%M:%S\"", &gm);
+	pp_pre_define(temp);
+	strftime(temp, sizeof temp, "__UTC_TIME_NUM__=%H%M%S", &gm);
+	pp_pre_define(temp);
+    }
+    
+    if (gm_p)
+	posix_time = posix_mktime(&gm);
+    else if (lt_p)
+	posix_time = posix_mktime(&lt);
+    else
+	posix_time = 0;
+
+    if (posix_time) {
+	snprintf(temp, sizeof temp, "__POSIX_TIME__=%"PRId64, posix_time);
+	pp_pre_define(temp);
+    }
+}
+
+static void define_macros_late(void)
+{
+    char temp[128];
+
+    snprintf(temp, sizeof(temp), "__OUTPUT_FORMAT__=%s\n",
+	     ofmt->shortname);
+    pp_pre_define(temp);
+}
+
 int main(int argc, char **argv)
 {
+    time(&official_compile_time);
+
     pass0 = 1;
     want_usage = terminate_after_phase = false;
     report_error = report_error_gnu;
@@ -179,6 +260,10 @@ int main(int argc, char **argv)
 
     register_output_formats();
 
+    /* Define some macros dependent on the runtime, but not
+       on the command line. */
+    define_macros_early();
+
     parse_cmdline(argc, argv);
 
     if (terminate_after_phase) {
@@ -197,12 +282,7 @@ int main(int argc, char **argv)
     eval_global_info(ofmt, lookup_label, &location);
 
     /* define some macros dependent of command-line */
-    {
-        char temp[64];
-        snprintf(temp, sizeof(temp), "__OUTPUT_FORMAT__=%s\n",
-                 ofmt->shortname);
-        pp_pre_define(temp);
-    }
+    define_macros_late();
 
     switch (operating_mode) {
     case op_depend_missing_ok:

test/time.asm

@@ -0,0 +1,10 @@
+	db __DATE__, 13, 10
+	db __TIME__, 13, 10
+	db __UTC_DATE__, 13, 10
+	db __UTC_TIME__, 13, 10
+	align 4
+	dd __DATE_NUM__
+	dd __TIME_NUM__
+	dd __UTC_DATE_NUM__
+	dd __UTC_TIME_NUM__
+	dd __POSIX_TIME__