Fix the max precision of the 'time' keyword

This commit backports the required fixes from ksh2020 for using millisecond precision with the 'time' keyword. The bugfix refactors a decent amount of code to rely on the BSD 'timeradd' and 'timersub' macros for calculating the total amount of time elapsed (as these aren't standard, they are selectively implemented in an iffe feature test for platforms without them). getrusage(3) is now preferred since it usually has higher precision than times(3) (the latter is used as a fallback). This patch can be extended with support for microsecond precision, although that is better left for a separate feature branch. There are three other fixes as well: src/lib/libast/features/time: - Test for getrusage with an iffe feature test rather than assume _sys_times == _lib_getrusage. src/cmd/ksh93/sh/xec.c: - A single percent at the end of a format specifier is now treated as a literal '%' (like in Bash). - Zero-pad seconds if seconds < 10. This was already done for the times builtin in commit 5c677a4, although it wasn't applied to the time keyword. - Backport the ksh2020 bugfix for the time keyword by using timeradd and timersub with gettimeofday (which is used with a timeofday macro). Prefer getrusage when it is available. src/cmd/ksh93/features/time: - Implement feature tests for the 'timeradd' and 'timersub' macros. - Do a feature test for getrusage like in the libast time test. src/cmd/ksh93/tests/basic.sh: - Add two tests for millisecond precision and the handling of '%' at the end of a format specifier.
ksh93 · Jul 11, 2020 · 68740bf · 68740bf
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commit 68740bf
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diff --git a/NEWS b/NEWS
@@ -3,6 +3,20 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2020-07-11:
+
+- Appending a lone percent to the end of a format specifier no longer
+  causes a syntax error. The extra percent will be treated as a literal
+  '%', like in Bash and zsh.
+
+- The 'time' keyword now has proper support for millisecond precision.
+  Although this feature was previously documented, the 'time' keyword
+  only supported up to centisecond precision, which caused a command
+  like the one below to return '0.000' on certain operating systems:
+  $ TIMEFORMAT='%3R'; time sleep .003
+
+- The 'time' keyword now zero-pads seconds less than ten (like mksh).
+
 2020-07-10:
 
 - Fixed a bug that caused types created with 'typeset -T' to throw an error

diff --git a/src/cmd/ksh93/features/time b/src/cmd/ksh93/features/time
@@ -1,5 +1,5 @@
-hdr	utime
-lib	gettimeofday,setitimer
+hdr	utime,sys/resource
+lib	getrusage,gettimeofday,setitimer
 mem	timeval.tv_usec sys/time.h
 tst	lib_2_timeofday note{ 2 arg gettimeofday() }end link{
 	#include <sys/types.h>
@@ -23,6 +23,7 @@ tst	lib_1_timeofday note{ 1 arg gettimeofday() }end link{
 cat{
 	#undef _def_time
 	#include	<times.h>
+	#include	<sys/time.h>
 	#define _def_time	1
 	#undef timeofday
 	#if _lib_2_timeofday
@@ -32,4 +33,27 @@ cat{
 	#define timeofday(p)	gettimeofday(p)
 	#endif
 	#endif
+	/* BSD timeradd and timersub macros */
+	#if !defined(timeradd)
+	#define	timeradd(tvp, uvp, vvp)						\
+	do {								\
+		(vvp)->tv_sec = (tvp)->tv_sec + (uvp)->tv_sec;		\
+		(vvp)->tv_usec = (tvp)->tv_usec + (uvp)->tv_usec;	\
+		if ((vvp)->tv_usec >= 1000000) {			\
+			(vvp)->tv_sec++;				\
+			(vvp)->tv_usec -= 1000000;			\
+		}							\
+	} while(0)
+	#endif
+	#if !defined(timersub)
+	#define	timersub(tvp, uvp, vvp)						\
+	do {								\
+		(vvp)->tv_sec = (tvp)->tv_sec - (uvp)->tv_sec;		\
+		(vvp)->tv_usec = (tvp)->tv_usec - (uvp)->tv_usec;	\
+		if ((vvp)->tv_usec < 0) {				\
+			(vvp)->tv_sec--;				\
+			(vvp)->tv_usec += 1000000;			\
+		}							\
+	} while(0)
+	#endif
 }end
diff --git a/src/cmd/ksh93/include/version.h b/src/cmd/ksh93/include/version.h
@@ -17,4 +17,4 @@
 *                  David Korn <[email protected]>                   *
 *                                                                      *
 ***********************************************************************/
-#define SH_RELEASE	"93u+m 2020-07-10"
+#define SH_RELEASE	"93u+m 2020-07-11"
diff --git a/src/cmd/ksh93/sh/xec.c b/src/cmd/ksh93/sh/xec.c
@@ -95,6 +95,52 @@ struct funenv
     }
 #endif /* !SHOPT_DEVFD */
 
+#if _lib_getrusage
+/* getrusage tends to have higher precision */
+static void get_cpu_times(Shell_t *shp, struct timeval *tv_usr, struct timeval *tv_sys)
+{
+	NOT_USED(shp);
+	struct rusage usage_self, usage_child;
+
+	getrusage(RUSAGE_SELF, &usage_self);
+	getrusage(RUSAGE_CHILDREN, &usage_child);
+	timeradd(&usage_self.ru_utime, &usage_child.ru_utime, tv_usr);
+	timeradd(&usage_self.ru_stime, &usage_child.ru_stime, tv_sys);
+}
+#else
+static void get_cpu_times(Shell_t *shp, struct timeval *tv_usr, struct timeval *tv_sys)
+{
+	struct tms cpu_times;
+	struct timeval tv1, tv2;
+	double dtime;
+
+	if(times(&cpu_times) == (clock_t)-1)
+		errormsg(SH_DICT, ERROR_exit(1), "times(3) failed: %s", strerror(errno));
+
+	dtime = (double)cpu_times.tms_utime / shp->gd->lim.clk_tck;
+	tv1.tv_sec = dtime / 60;
+	tv1.tv_usec = 1000000 * (dtime - tv1.tv_sec);
+	dtime = (double)cpu_times.tms_cutime / shp->gd->lim.clk_tck;
+	tv2.tv_sec = dtime / 60;
+	tv2.tv_usec = 1000000 * (dtime - tv2.tv_sec);
+	timeradd(&tv1, &tv2, tv_usr);
+
+	dtime = (double)cpu_times.tms_stime / shp->gd->lim.clk_tck;
+	tv1.tv_sec = dtime / 60;
+	tv1.tv_usec = 1000000 * (dtime - tv1.tv_sec);
+	dtime = (double)cpu_times.tms_cstime / shp->gd->lim.clk_tck;
+	tv2.tv_sec = dtime / 60;
+	tv2.tv_usec = 1000000 * (dtime - tv2.tv_sec);
+	timeradd(&tv1, &tv2, tv_sys);
+}
+#endif
+
+/* 'inline' is commented out because C89 doesn't have it */
+static /*inline*/ double timeval_to_double(struct timeval tv)
+{
+	return (double)tv.tv_sec + ((double)tv.tv_usec / 1000000.0);
+}
+
 /*
  * The following two functions allow command substitution for non-builtins
  * to use a pipe and to wait for the pipe to close before restoring to a
@@ -182,78 +228,103 @@ static void iounpipe(Shell_t *shp)
 /*
  * print time <t> in h:m:s format with precision <p>
  */
-static void     l_time(Sfio_t *outfile,register clock_t t,int p)
+static void l_time(Sfio_t *outfile, struct timeval *tv, int precision)
 {
-	register int  min, sec, frac;
-	register int hr;
-	if(p)
-	{
-		frac = t%shgd->lim.clk_tck;
-		frac = (frac*100)/shgd->lim.clk_tck;
-	}
-	t /= shgd->lim.clk_tck;
-	sec = t%60;
-	t /= 60;
-	min = t%60;
-	if(hr=t/60)
-		sfprintf(outfile,"%dh",hr);
-	if(p)
-		sfprintf(outfile,"%dm%d%c%0*ds",min,sec,GETDECIMAL(0),p,frac);
+	int hr = tv->tv_sec / (60 * 60);
+	int min = (tv->tv_sec / 60) % 60;
+	int sec = tv->tv_sec % 60;
+	int frac = tv->tv_usec;
+
+	/* scale fraction from micro to milli, centi, or deci second according to precision */
+	int n;
+	for(n = 3 + (3 - precision); n > 0; --n)
+		frac /= 10;
+
+	if(hr)
+		sfprintf(outfile, "%dh", hr);
+	if(precision)
+		sfprintf(outfile, "%dm%02d%c%0*ds", min, sec, GETDECIMAL(0), precision, frac);
 	else
-		sfprintf(outfile,"%dm%ds",min,sec);
+		sfprintf(outfile,"%dm%02ds",min,sec);
 }
 
-static int p_time(Shell_t *shp, Sfio_t *out, const char *format, clock_t *tm)
+#define TM_REAL_IDX 0
+#define TM_USR_IDX 1
+#define TM_SYS_IDX 2
+
+static void p_time(Shell_t *shp, Sfio_t *out, const char *format, struct timeval tm[3])
 {
-	int		c,p,l,n,offset = staktell();
+	int		c,n,offset = staktell();
 	const char	*first;
-	double		d;
+	struct timeval tv_cpu_sum;
+	struct timeval *tvp;
 	Stk_t		*stkp = shp->stk;
-	for(first=format ; c= *format; format++)
+	for(first=format ; *format; format++)
 	{
+		c = *format;
 		if(c!='%')
 			continue;
+		unsigned char l_modifier = 0;
+		int precision = 3;
+
 		sfwrite(stkp, first, format-first);
-		n = l = 0;
-		p = 3;
-		if((c= *++format) == '%')
+		c = *++format;
+		if(c=='\0')
+		{
+			/* If a lone percent is the last character of the format pretend
+			   the user had written `%%` for a literal percent */
+			sfwrite(stkp, "%", 1);
+			first = format + 1;
+			break;
+		}
+		else if(c=='%')
 		{
 			first = format;
 			continue;
 		}
 		if(c>='0' && c <='9')
 		{
-			p = (c>'3')?3:(c-'0');
+			precision = (c>'3')?3:(c-'0');
 			c = *++format;
 		}
-		else if(c=='P')
+		if(c=='P')
 		{
-			if(d=tm[0])
-				d = 100.*(((double)(tm[1]+tm[2]))/d);
-			p = 2;
-			goto skip;
+			struct timeval tv_real = tm[TM_REAL_IDX];
+			struct timeval tv_cpu;
+			timeradd(&tm[TM_USR_IDX], &tm[TM_SYS_IDX], &tv_cpu);
+
+			double d = timeval_to_double(tv_real);
+			if(d)
+				d = 100.0 * timeval_to_double(tv_cpu) / d;
+			sfprintf(stkp, "%.*f", precision, d);
+			first = format + 1;
+			continue;
 		}
 		if(c=='l')
 		{
-			l = 1;
+			l_modifier = 1;
 			c = *++format;
 		}
-		if(c=='U')
-			n = 1;
+		if(c=='R')
+			tvp = &tm[TM_REAL_IDX];
+		else if(c=='U')
+			tvp = &tm[TM_USR_IDX];
 		else if(c=='S')
-			n = 2;
-		else if(c!='R')
+			tvp = &tm[TM_SYS_IDX];
+		else
 		{
-			stkseek(stkp,offset);
 			errormsg(SH_DICT,ERROR_exit(0),e_badtformat,c);
-			return(0);
+			continue;
 		}
-		d = (double)tm[n]/shp->gd->lim.clk_tck;
-	skip:
-		if(l)
-			l_time(stkp, tm[n], p);
+		if(l_modifier)
+			l_time(stkp, tvp, precision);
 		else
-			sfprintf(stkp,"%.*f",p, d);
+		{
+			/* scale fraction from micro to milli, centi, or deci second according to precision */
+			int n, frac = tvp->tv_usec;
+			for(n = 3 + (3 - precision); n > 0; --n) frac /= 10;
+			sfprintf(stkp, "%d.%0*d", tvp->tv_sec, precision, frac);
+		}
 		first = format+1;
 	}
 	if(format>first)
@@ -262,7 +333,6 @@ static int p_time(Shell_t *shp, Sfio_t *out, const char *format, clock_t *tm)
 	n = stktell(stkp)-offset;
 	sfwrite(out,stkptr(stkp,offset),n);
 	stkseek(stkp,offset);
-	return(n);
 }
 
 #if SHOPT_OPTIMIZE
@@ -2577,14 +2647,9 @@ int sh_exec(register const Shnode_t *t, int flags)
 		    case TTIME:
 		    {
 			/* time the command */
-			struct tms before,after;
 			const char *format = e_timeformat;
-			clock_t at, tm[3];
-#ifdef timeofday
-			struct timeval tb,ta;
-#else
-			clock_t bt;
-#endif	/* timeofday */
+			struct timeval ta, tb, tm[3];
+			struct timeval before_usr, before_sys, after_usr, after_sys;
 #if SHOPT_COSHELL
 			if(shp->inpool)
 			{
@@ -2599,42 +2664,26 @@ int sh_exec(register const Shnode_t *t, int flags)
 				shp->exitval = !shp->exitval;
 				break;
 			}
+			timeofday(&tb);
+			get_cpu_times(shp, &before_usr, &before_sys);
 			if(t->par.partre)
 			{
-				long timer_on;
 				if(shp->subshell && shp->comsub==1)
 					sh_subfork();
-				timer_on = sh_isstate(SH_TIMING);
-#ifdef timeofday
-				timeofday(&tb);
-				times(&before);
-#else
-				bt = times(&before);
-#endif	/* timeofday */
+				long timer_on = sh_isstate(SH_TIMING);
 				job.waitall = 1;
 				sh_onstate(SH_TIMING);
 				sh_exec(t->par.partre,OPTIMIZE);
 				if(!timer_on)
 					sh_offstate(SH_TIMING);
 				job.waitall = 0;
 			}
-			else
-			{
-#ifndef timeofday
-				bt = 0;
-#endif	/* timeofday */
-				before.tms_utime = before.tms_cutime = 0;
-				before.tms_stime = before.tms_cstime = 0;
-			}
-#ifdef timeofday
-			times(&after);
+			get_cpu_times(shp, &after_usr, &after_sys);
 			timeofday(&ta);
-			at = shp->gd->lim.clk_tck*(ta.tv_sec-tb.tv_sec);
-			at +=  ((shp->gd->lim.clk_tck*(((1000000L/2)/shp->gd->lim.clk_tck)+(ta.tv_usec-tb.tv_usec)))/1000000L);
-#else
-			at = times(&after) - bt;
-#endif	/* timeofday */
-			tm[0] = at;
+			timersub(&ta, &tb, &tm[TM_REAL_IDX]); /* calculate elapsed real-time */
+			timersub(&after_usr, &before_usr, &tm[TM_USR_IDX]);
+			timersub(&after_sys, &before_sys, &tm[TM_SYS_IDX]);
+
 			if(t->par.partre)
 			{
 				Namval_t *np = nv_open("TIMEFORMAT",shp->var_tree,NV_NOADD);
@@ -2648,10 +2697,6 @@ int sh_exec(register const Shnode_t *t, int flags)
 			}
 			else
 				format = strchr(format+1,'\n')+1;
-			tm[1] = after.tms_utime - before.tms_utime;
-			tm[1] += after.tms_cutime - before.tms_cutime;
-			tm[2] = after.tms_stime - before.tms_stime;
-			tm[2] += after.tms_cstime - before.tms_cstime;
 			if(format && *format)
 				p_time(shp,sfstderr,sh_translate(format),tm);
 			break;

diff --git a/src/cmd/ksh93/tests/basic.sh b/src/cmd/ksh93/tests/basic.sh
@@ -552,5 +552,26 @@ $SHELL 2> /dev/null -c $'for i;\ndo :;done' || err_exit 'for i ; <newline> not v
 	"$SHELL" main.ksh 2>/dev/null
 ) || err_exit "crash when sourcing multiple files (exit status $?)"
 
+# ======
+# The time keyword should correctly handle millisecond precision.
+# This can be checked by verifying the last digit is not a zero
+# when 'time sleep .002' is run.
+result=$(
+	TIMEFORMAT=$'\%3R'
+	redirect 2>&1
+	time sleep .002
+)
+[[ ${result: -1} == 0 ]] && err_exit "the 'time' keyword doesn't properly support millisecond precision"
+
+# A single '%' after a format specifier should not be a syntax
+# error (it should be treated as a literal '%').
+IFS=' '
+result=( $(
+	TIMEFORMAT=$'%0S%'
+	redirect 2>&1
+	time :
+) )
+[[ ${result[4]} == bad ]] && err_exit "'%' is not treated literally when placed after a format specifier"
+
 # ======
 exit $((Errors<125?Errors:125))
diff --git a/src/lib/libast/features/time b/src/lib/libast/features/time
@@ -1,8 +1,13 @@
 set	prototyped
-lib	nanosleep,usleep,_strftime
+lib	getrusage,nanosleep,usleep,_strftime
 typ	clock_t = uint32_t
 typ	time_t = uint32_t
 
+if sys resource {
+	#include <sys/resource.h>
+}
+endif
+
 if sys time {
 	#include <sys/time.h>
 }