From: Ralph Corderoy <ralph@inputplus.co.uk>
Date: Mon, 31 Oct 2016 18:18:07 +0000 (+0000)
Subject: mhbuild's fgetstr(): simplify source, logic untouched.
X-Git-Url: https://diplodocus.org/git/nmh/commitdiff_plain/f139ce94a95fd895d8b4b74826660ab076ed5129?hp=36c39624a208467bf2bd1d7155b85edcfc5b07ae

mhbuild's fgetstr(): simplify source, logic untouched.

The tests aren't getting 100% coverage and the nested assignments make
it harder to see what's happening, and what needs to happen to gain
coverage.  Hoist invariants so it's clear they're such to the reader and
not just the compiler.
---

diff --git a/uip/mhbuildsbr.c b/uip/mhbuildsbr.c
index fc90dc01..df346fec 100644
--- a/uip/mhbuildsbr.c
+++ b/uip/mhbuildsbr.c
@@ -612,23 +612,26 @@ static char *
 fgetstr (char *s, int n, FILE *stream)
 {
     char *cp, *ep;
-    int o_n = n;
 
+    ep = s + n;
     while(1) {
-	for (ep = (cp = s) + o_n; cp < ep; ) {
-	    int i;
+	for (cp = s; cp < ep;) {
+	    int len;
 
 	    if (!fgets (cp, n, stream))
-		return (cp != s ? s : NULL);
+                return cp == s ? NULL : s; /* "\\\nEOF" ignored. */
 
 	    if (cp == s && *cp != '#')
-		return s;
+		return s; /* Plaintext line. */
 
-	    cp += (i = strlen (cp)) - 1;
-	    if (i <= 1 || *cp-- != '\n' || *cp != '\\')
+	    len = strlen(cp);
+	    if (len <= 1)
+		break; /* Can't contain "\\\n". */
+	    cp += len - 1; /* Just before NUL. */
+	    if (*cp-- != '\n' || *cp != '\\')
 		break;
-	    *cp = '\0';
-	    n -= (i - 2);
+	    *cp = '\0'; /* Erase the trailing "\\\n". */
+	    n -= (len - 2);
 	}
 
 	if (strcmp(s, "#on\n") == 0) {
@@ -638,11 +641,9 @@ fgetstr (char *s, int n, FILE *stream)
 	} else if (strcmp(s, "#pop\n") == 0) {
 	    directive_pop();
 	} else {
-	    break;
+	    return s;
 	}
     }
-
-    return s;
 }