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arithmetic: Fix the octal leading zero mess (#337)

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In C/POSIX arithmetic, a leading 0 denotes an octal number, e.g.
010 == 8. But this is not a desirable feature as it can cause
problems with processing things like dates with a leading zero.
In ksh, you should use 8#10 instead ("10" with base 8).

It would be tolerable if ksh at least implemented it consistently.
But AT&T made an incredible mess of it. For anyone who is not
intimately familiar with ksh internals, it is inscrutable where
arithmetic evaluation special-cases a leading 0 and where it
doesn't. Here are just some of the surprises/inconsistencies:

1. The AT&T maintainers tried to honour a leading 0 inside of
   ((...)) and $((...)) and not for arithmetic contexts outside it,
   but even that inconsistency was never quite consistent.

2. Since 2010-12-12, $((x)) and $(($x)) are different:
      $ /bin/ksh -c 'x=010; echo $((x)) $(($x))'
      10 8
   That's a clear violation of both POSIX and the principle of
   least astonishment. $((x)) and $(($x)) should be the same in
   all cases.

3. 'let' with '-o letoctal' acts in this bizarre way:
      $ set -o letoctal; x=010; let "y1=$x" "y2=010"; echo $y1 $y2
      10 8
   That's right, 'let y=$x' is different from 'let y=010' even
   when $x contains the same string value '010'! This violates
   established shell grammar on the most basic level.

This commit introduces consistency. By default, ksh now acts like
mksh and zsh: the octal leading zero is disabled in all arithmetic
contexts equally. In POSIX mode, it is enabled equally.

The one exception is the 'let' built-in, where this can still be
controlled independently with the letoctal option as before (but,
because letoctal is synched with posix when switching that on/off,
it's consistent by default).

We're also removing the hackery that causes variable expansions for
the 'let' builtin to be quietly altered, so that 'x=010; let y=$x'
now does the same as 'let y=010' even with letoctal on.

Various files:
- Get rid of now-redundant sh.inarith (shp->inarith) flag, as we're
  no longer distinguishing between being inside or outside ((...)).

src/cmd/ksh93/sh/arith.c:
- arith(): Let disabling POSIX octal constants by skipping leading
  zeros depend on either the letoctal option being off (if we're
  running the "let" built-in") or the posix option being off.
- sh_strnum(): Preset a base of 10 for strtonll(3) depending on the
  posix or letoctal option being off, not on the sh.inarith flag.

src/cmd/ksh93/include/argnod.h,
src/cmd/ksh93/sh/args.c,
src/cmd/ksh93/sh/macro.c:
- Remove astonishing hackery that violated shell grammar for 'let'.

src/cmd/ksh93/sh/name.c (nv_getnum()),
src/cmd/ksh93/sh/nvdisc.c (nv_getn()):
- Remove loops for skipping leading zeroes that included a broken
  check for justify/zerofill attributes, thereby fixing this bug:
	$ typeset -Z x=0x15; echo $((x))
	-ksh: x15: parameter not set
  Even if this code wasn't redundant before, it is now: sh_arith()
  is called immediately after the removed code and it ignores
  leading zeroes via sh_strnum() and strtonll(3).

Resolves: https://github.com/ksh93/ksh/issues/334
This commit is contained in:
Martijn Dekker 2021-11-17 03:24:18 +00:00
parent 257eea612a
commit c734568b02
14 changed files with 86 additions and 93 deletions
Download patch file Download diff file Expand all files Collapse all files

28
src/cmd/ksh93/sh/macro.c
View file

@ -74,8 +74,6 @@ typedef struct _mac_
char patfound; /* set if pattern character found */
char assign; /* set for assignments */
char arith; /* set for ((...)) */
char let; /* set when expanding let arguments */
char zeros; /* strip leading zeros when set */
char arrayok; /* $x[] ok for arrays */
char subcopy; /* set when copying subscript */
int dotdot; /* set for .. in subscript */
@ -161,7 +159,6 @@ char *sh_mactrim(Shell_t *shp, char *str, register int mode)
savemac = *mp;
stkseek(stkp,0);
mp->arith = (mode==3);
mp->let = 0;
shp->argaddr = 0;
mp->pattern = (mode==1||mode==2);
mp->patfound = 0;
@ -219,7 +216,6 @@ int sh_macexpand(Shell_t* shp, register struct argnod *argp, struct argnod **arg
mp->arghead = arghead;
mp->quoted = mp->lit = mp->quote = 0;
mp->arith = ((flag&ARG_ARITH)!=0);
mp->let = ((flag&ARG_LET)!=0);
mp->split = !(flag&ARG_ASSIGN);
mp->assign = !mp->split;
mp->pattern = mp->split && !(flag&ARG_NOGLOB) && !sh_isoption(SH_NOGLOB);
@ -279,7 +275,7 @@ void sh_machere(Shell_t *shp,Sfio_t *infile, Sfio_t *outfile, char *string)
stkseek(stkp,0);
shp->argaddr = 0;
mp->sp = outfile;
mp->split = mp->assign = mp->pattern = mp->patfound = mp->lit = mp->arith = mp->let = 0;
mp->split = mp->assign = mp->pattern = mp->patfound = mp->lit = mp->arith = 0;
mp->quote = 1;
mp->ifsp = nv_getval(sh_scoped(shp,IFSNOD));
mp->ifs = ' ';
@ -1101,7 +1097,6 @@ static int varsub(Mac_t *mp)
int var=1,addsub=0,oldpat=mp->pattern,idnum=0,flag=0,d;
Stk_t *stkp = mp->shp->stk;
retry1:
mp->zeros = 0;
idbuff[0] = 0;
idbuff[1] = 0;
c = fcmbget(&LEN);
@ -1466,9 +1461,6 @@ retry1:
else
v = nv_getval(np);
mp->atmode = (v && mp->quoted && mode=='@');
/* special case --- ignore leading zeros */
if((mp->let || (mp->arith&&nv_isattr(np,(NV_LJUST|NV_RJUST|NV_ZFILL)))) && !nv_isattr(np,NV_INTEGER) && (offset==0 || isspace(c) || strchr(",.+-*/=%&|^?!<>",c)))
mp->zeros = 1;
}
if(savptr==stakptr(0))
stkseek(stkp,offset);
@ -1621,7 +1613,6 @@ retry1:
int split = mp->split;
int quoted = mp->quoted;
int arith = mp->arith;
int zeros = mp->zeros;
int assign = mp->assign;
if(newops)
{
@ -1638,7 +1629,7 @@ retry1:
mp->split = 0;
mp->quoted = 0;
mp->assign &= ~1;
mp->arith = mp->zeros = 0;
mp->arith = 0;
newquote = 0;
}
else if(c=='?' || c=='=')
@ -1650,7 +1641,6 @@ retry1:
mp->split = split;
mp->quoted = quoted;
mp->arith = arith;
mp->zeros = zeros;
mp->assign = assign;
/* add null byte */
sfputc(stkp,0);
@ -2111,7 +2101,6 @@ static void comsubst(Mac_t *mp,register Shnode_t* t, int type)
t = sh_dolparen((Lex_t*)mp->shp->lex_context);
if(t && t->tre.tretyp==TARITH)
{
mp->shp->inarith = 1;
fcsave(&save);
if(t->ar.arcomp)
num = arith_exec(t->ar.arcomp);
@ -2119,7 +2108,6 @@ static void comsubst(Mac_t *mp,register Shnode_t* t, int type)
num = sh_arith(mp->shp,t->ar.arexpr->argval);
else
num = sh_arith(mp->shp,sh_mactrim(mp->shp,t->ar.arexpr->argval,3));
mp->shp->inarith = 0;
out_offset:
stkset(stkp,savptr,savtop);
*mp = savemac;
@ -2330,18 +2318,6 @@ static void mac_copy(register Mac_t *mp,register const char *str, register int s
Stk_t *stkp=mp->shp->stk;
int oldpat = mp->pattern;
nopat = (mp->quote||(mp->assign==1)||mp->arith);
if(mp->zeros)
{
/* prevent leading 0's from becoming octal constants */
while(size>1 && *str=='0')
{
if(str[1]=='x' || str[1]=='X')
break;
str++,size--;
}
mp->zeros = 0;
cp = str;
}
if(mp->sp)
sfwrite(mp->sp,str,size);
else if(mp->pattern>=2 || (mp->pattern && nopat) || mp->assign==3)