Simplify malloc(3)/realloc(3) usage

At a number of places in this code base, a memory block gets
allocated with malloc(3) first and then grown with realloc(3) if
necessary. But, if the pointer to the block is initialised to NULL,
then realloc(3) can always be used, because realloc(3) with a
pointer argument of NULL is equivalent to malloc(3). This allows
for a simplification at various points in the code.

We can also eliminate redundant typecasts while we're at it (these
are not needed as of the change to C90).

src/cmd/ksh93/sh/init.c

@@ -909,21 +909,9 @@ void sh_setmatch(const char *v, int vsize, int nmatch, int match[], int index)
 		index *= 2*mp->nmatch;
 		i = (index+2*mp->nmatch)*sizeof(match[0]);
 		if(i >= mp->msize)
-		{
-			if(mp->msize)
-				mp->match = (int*)sh_realloc(mp->match,2*i);
-			else
-				mp->match = (int*)sh_malloc(2*i);
-			mp->msize = 2*i;
-		}
+			mp->match = sh_realloc(mp->match, mp->msize = 2*i);
 		if(vsize >= mp->vsize)
-		{
-			if(mp->vsize)
-				mp->val = (char*)sh_realloc(mp->val,x=2*vsize);
-			else
-				mp->val =  (char*)sh_malloc(x=vsize+1);
-			mp->vsize = x;
-		}
+			mp->val = sh_realloc(mp->val, mp->vsize = mp->vsize ? 2 * vsize : vsize + 1);
 		memcpy(mp->match+index,match,nmatch*2*sizeof(match[0]));
 		for(i=0; i < 2*nmatch; i++)
 		{

src/cmd/ksh93/sh/lex.c

@@ -2503,9 +2503,6 @@ static void setupalias(Lex_t *lp, const char *string,Namval_t *np)
 static int stack_grow(void)
 {
 	lex_max += STACK_ARRAY;
-	if(lex_match)
-		lex_match = (int*)sh_realloc((char*)lex_match,sizeof(int)*lex_max);
-	else
-		lex_match = (int*)sh_malloc(sizeof(int)*STACK_ARRAY);
+	lex_match = sh_realloc(lex_match,sizeof(int)*lex_max);
 	return 1;
 }

src/cmd/ksh93/sh/name.c

@@ -105,13 +105,7 @@ static char *getbuf(size_t len)
 	static char *buf;
 	static size_t buflen;
 	if(buflen < len)
-	{
-		if(buflen==0)
-			buf = (char*)sh_malloc(len);
-		else
-			buf = (char*)sh_realloc(buf,len);
-		buflen = len;
-	}
+		buf = sh_realloc(buf, buflen = len);
 	return buf;
 }
 
@@ -1474,13 +1468,7 @@ Namval_t *nv_open(const char *name, Dt_t *root, int flags)
 			xp->len = strlen(name);
 		c = roundof(xp->len+1,32);
 		if(c > xp->size)
-		{
-			if(xp->size==0)
-				xp->name = sh_malloc(c);
-			else
-				xp->name = sh_realloc(xp->name,c);
-			xp->size = c;
-		}
+			xp->name = sh_realloc(xp->name, xp->size = c);
 		memcpy(xp->name,name,xp->len);
 		xp->name[xp->len] = 0;
 		xp->root = root;

src/lib/libast/disc/sfdcdos.c

@@ -157,16 +157,8 @@ static ssize_t dos_read(Sfio_t *iop, void *buff, size_t size, Sfdisc_t* disc)
 		}
 	}
 	/* save original discipline inside buffer */
-	if(count>dp->bsize)
-	{
-		if(dp->bsize==0)
-			dp->buff = malloc(count);
-		else
-			dp->buff = realloc(dp->buff,count);
-		dp->bsize = count;
-		if(!dp->buff)
-			return -1;
-	}
+	if(count > dp->bsize && !(dp->buff = realloc(dp->buff, dp->bsize = count)))
+		return -1;
 	memcpy(dp->buff, cp, count);
 	count=1;
 	while(1)

src/lib/libast/regex/reginit.c

@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1985-2011 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2023 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2024 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 2.0                  *
 *                                                                      *
@@ -385,14 +385,11 @@ alloc(regdisc_t* disc, void* p, size_t n)
 			return NULL;
 		return (*disc->re_resizef)(disc->re_resizehandle, p, n);
 	}
-	else if (!n)
+	if (!n)
 	{
 		if (!(disc->re_flags & REG_NOFREE))
 			free(p);
 		return NULL;
 	}
-	else if (p)
-		return realloc(p, n);
-	else
-		return malloc(n);
+	return realloc(p, n);
 }

src/lib/libast/sfio/sfexcept.c

@@ -75,10 +75,7 @@ int _sfexcept(Sfio_t*	f,	/* stream where the exception happened */
 			if((io -= size) <= 0)
 				io = SFIO_GRAIN;
 			size = ((size+io+SFIO_GRAIN-1)/SFIO_GRAIN)*SFIO_GRAIN;
-			if(f->size > 0)
-				data = (uchar*)realloc((char*)f->data,size);
-			else	data = (uchar*)malloc(size);
-			if(!data)
+			if(!(data = realloc(f->data,size)))
 				goto chk_stack;
 			f->endb = data + size;
 			f->next = data + (f->next - f->data);