string: test cleanups

Tests printed too much output on broken string function
and the output was not entirely useful.

Added a new header file with some common logic for
printing buffers nicely.

In str* tests len now means string length (not buffer
size which was confusing).

15 files changed, 278 insertions, 216 deletions

diff --git a/string/test/memchr.c b/string/test/memchr.c
index 391c9df..15531c6 100644
--- a/string/test/memchr.c
+++ b/string/test/memchr.c
@@ -11,6 +11,7 @@
 #include <string.h>
 #include <limits.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -32,9 +33,6 @@ F(__memchr_arm)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define SP 512
 #define LEN 250000
@@ -57,6 +55,8 @@ static void test(const struct fun *fun, int align, size_t seekpos,
 	int i;
 	void *p;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (array_len > LEN || seekpos >= array_len || align >= A)
 		abort();
 
@@ -71,8 +71,8 @@ static void test(const struct fun *fun, int align, size_t seekpos,
 	if (p != f) {
 		ERR("%s(%p,0x%02x,%zu) returned %p\n",
 			fun->name, s, seekchar, param_len, p);
-		ERR("expected: %p\n", f);
-		abort();
+		printf("expected: %p\n", f);
+		quote("str", s, param_len);
 	}
 }
 
@@ -80,7 +80,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int a = 0; a < A; a++) {
 			for (int n = 0; n < 100; n++)
 				for (int sp = 0; sp < n-1; sp++)
@@ -93,8 +93,8 @@ int main()
 				test(funtab+i, a, LEN-1-n, LEN, MAX_LEN-n);
 			}
 		}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/memcmp.c b/string/test/memcmp.c
index 114f1d7..28160ef 100644
--- a/string/test/memcmp.c
+++ b/string/test/memcmp.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -28,9 +29,6 @@ F(__memcmp_aarch64_sve)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
 static unsigned char s1buf[LEN+2*A];
@@ -41,7 +39,7 @@ static void *alignup(void *p)
 	return (void*)(((uintptr_t)p + A-1) & -A);
 }
 
-static void test(const struct fun *fun, int s1align, int s2align, int len, int diffpos)
+static void test(const struct fun *fun, int s1align, int s2align, int len, int diffpos, int delta)
 {
 	unsigned char *src1 = alignup(s1buf);
 	unsigned char *src2 = alignup(s2buf);
@@ -49,25 +47,29 @@ static void test(const struct fun *fun, int s1align, int s2align, int len, int d
 	unsigned char *s2 = src2 + s2align;
 	int r;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || s1align >= A || s2align >= A)
 		abort();
-	if (diffpos && diffpos >= len)
+	if (diffpos >= len)
+		abort();
+	if ((diffpos < 0) != (delta == 0))
 		abort();
 
 	for (int i = 0; i < len+A; i++)
 		src1[i] = src2[i] = '?';
 	for (int i = 0; i < len; i++)
 		s1[i] = s2[i] = 'a' + i%23;
-	if (diffpos)
-		s1[diffpos]++;
+	if (delta)
+		s1[diffpos] += delta;
 
 	r = fun->fun(s1, s2, len);
 
-	if ((!diffpos && r != 0) || (diffpos && r == 0)) {
+	if ((delta == 0 && r != 0) || (delta > 0 && r <= 0) || (delta < 0 && r >= 0)) {
 		ERR("%s(align %d, align %d, %d) failed, returned %d\n",
 			fun->name, s1align, s2align, len, r);
-		ERR("src1: %.*s\n", s1align+len+1, src1);
-		ERR("src2: %.*s\n", s2align+len+1, src2);
+		quoteat("src1", src1, len+A, diffpos);
+		quoteat("src2", src2, len+A, diffpos);
 	}
 }
 
@@ -75,21 +77,27 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int d = 0; d < A; d++)
 			for (int s = 0; s < A; s++) {
 				int n;
-				for (n = 0; n < 100; n++) {
-					test(funtab+i, d, s, n, 0);
-					test(funtab+i, d, s, n, n / 2);
+				test(funtab+i, d, s, 0, -1,  0);
+				test(funtab+i, d, s, 1, -1,  0);
+				test(funtab+i, d, s, 1,  0, -1);
+				test(funtab+i, d, s, 1,  0,  1);
+				for (n = 2; n < 100; n++) {
+					test(funtab+i, d, s, n, -1, 0);
+					test(funtab+i, d, s, n, 0, -1);
+					test(funtab+i, d, s, n, n - 1, -1);
+					test(funtab+i, d, s, n, n / 2, 1);
 				}
 				for (; n < LEN; n *= 2) {
-					test(funtab+i, d, s, n, 0);
-					test(funtab+i, d, s, n, n / 2);
+					test(funtab+i, d, s, n, -1, 0);
+					test(funtab+i, d, s, n, n / 2, -1);
 				}
 			}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/memcpy.c b/string/test/memcpy.c
index 8572452..bf1bbae 100644
--- a/string/test/memcpy.c
+++ b/string/test/memcpy.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -30,9 +31,6 @@ F(__memcpy_arm)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
 static unsigned char dbuf[LEN+2*A];
@@ -55,6 +53,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	void *p;
 	int i;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || dalign >= A || salign >= A)
 		abort();
 	for (i = 0; i < len+A; i++) {
@@ -70,8 +70,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	for (i = 0; i < len+A; i++) {
 		if (dst[i] != want[i]) {
 			ERR("%s(align %d, align %d, %d) failed\n", fun->name, dalign, salign, len);
-			ERR("got : %.*s\n", dalign+len+1, dst);
-			ERR("want: %.*s\n", dalign+len+1, want);
+			quoteat("got", dst, len+A, i);
+			quoteat("want", want, len+A, i);
 			break;
 		}
 	}
@@ -81,7 +81,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int d = 0; d < A; d++)
 			for (int s = 0; s < A; s++) {
 				int n;
@@ -90,8 +90,8 @@ int main()
 				for (; n < LEN; n *= 2)
 					test(funtab+i, d, s, n);
 			}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/memmove.c b/string/test/memmove.c
index 7891b14..04f4c3c 100644
--- a/string/test/memmove.c
+++ b/string/test/memmove.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -28,9 +29,6 @@ F(__memmove_aarch64_simd)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
 static unsigned char dbuf[LEN+2*A];
@@ -53,6 +51,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	void *p;
 	int i;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || dalign >= A || salign >= A)
 		abort();
 	for (i = 0; i < len+A; i++) {
@@ -68,8 +68,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	for (i = 0; i < len+A; i++) {
 		if (dst[i] != want[i]) {
 			ERR("%s(align %d, align %d, %d) failed\n", fun->name, dalign, salign, len);
-			ERR("got : %.*s\n", dalign+len+1, dst);
-			ERR("want: %.*s\n", dalign+len+1, want);
+			quoteat("got", dst, len+A, i);
+			quoteat("want", want, len+A, i);
 			break;
 		}
 	}
@@ -78,13 +78,15 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 static void test_overlap(const struct fun *fun, int dalign, int salign, int len)
 {
 	unsigned char *src = alignup(sbuf);
-	unsigned char *dst = alignup(sbuf);
+	unsigned char *dst = src;
 	unsigned char *want = wbuf;
 	unsigned char *s = src + salign;
 	unsigned char *d = dst + dalign;
 	unsigned char *w = wbuf + dalign;
 	void *p;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || dalign >= A || salign >= A)
 		abort();
 
@@ -92,16 +94,9 @@ static void test_overlap(const struct fun *fun, int dalign, int salign, int len)
 		src[i] = want[i] = '?';
 
 	for (int i = 0; i < len; i++)
-		s[i] = w[i] = 'a' + i%23;
-
-	/* Copy the potential overlap range.  */
-	if (s < d) {
-		for (int i = 0; i < (uintptr_t)d-(uintptr_t)s; i++)
-			want[salign+i] = src[salign+i];
-	} else {
-		for (int i = 0; i < (uintptr_t)s-(uintptr_t)d; i++)
-			want[len + dalign + i] = src[len + dalign + i];
-	}
+		s[i] = want[salign+i] = 'a' + i%23;
+	for (int i = 0; i < len; i++)
+		w[i] = s[i];
 
 	p = fun->fun(d, s, len);
 	if (p != d)
@@ -109,9 +104,8 @@ static void test_overlap(const struct fun *fun, int dalign, int salign, int len)
 	for (int i = 0; i < len+A; i++) {
 		if (dst[i] != want[i]) {
 			ERR("%s(align %d, align %d, %d) failed\n", fun->name, dalign, salign, len);
-			ERR("got : %.*s\n", dalign+len+1, dst);
-			ERR("want: %.*s\n", dalign+len+1, want);
-			abort();
+			quoteat("got", dst, len+A, i);
+			quoteat("want", want, len+A, i);
 			break;
 		}
 	}
@@ -119,11 +113,9 @@ static void test_overlap(const struct fun *fun, int dalign, int salign, int len)
 
 int main()
 {
-	test_overlap(funtab+0, 2, 1, 1);
-
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int d = 0; d < A; d++)
 			for (int s = 0; s < A; s++) {
 				int n;
@@ -136,8 +128,8 @@ int main()
 					test_overlap(funtab+i, d, s, n);
 				}
 			}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/memset.c b/string/test/memset.c
index 48c10fa..8b05bd6 100644
--- a/string/test/memset.c
+++ b/string/test/memset.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -27,9 +28,6 @@ F(__memset_arm)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
 static unsigned char sbuf[LEN+2*A];
@@ -39,12 +37,6 @@ static void *alignup(void *p)
 	return (void*)(((uintptr_t)p + A-1) & -A);
 }
 
-static void err(const char *name, unsigned char *src, int salign, int c, int len)
-{
-	ERR("%s(align %d, %d, %d) failed\n", name, salign, c, len);
-	ERR("got : %.*s\n", salign+len+1, src);
-}
-
 static void test(const struct fun *fun, int salign, int c, int len)
 {
 	unsigned char *src = alignup(sbuf);
@@ -52,14 +44,14 @@ static void test(const struct fun *fun, int salign, int c, int len)
 	void *p;
 	int i;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || salign >= A)
 		abort();
 	for (i = 0; i < len+A; i++)
 		src[i] = '?';
 	for (i = 0; i < len; i++)
 		s[i] = 'a' + i%23;
-	for (; i<len%A; i++)
-		s[i] = '*';
 
 	p = fun->fun(s, c, len);
 	if (p != s)
@@ -67,19 +59,22 @@ static void test(const struct fun *fun, int salign, int c, int len)
 
 	for (i = 0; i < salign; i++) {
 		if (src[i] != '?') {
-			err(fun->name, src, salign, c, len);
+			ERR("%s(align %d, %d, %d) failed\n", fun->name, salign, c, len);
+			quoteat("got", src, len+A, i);
 			return;
 		}
 	}
-	for (i = salign; i < len; i++) {
+	for (; i < salign+len; i++) {
 		if (src[i] != (unsigned char)c) {
-			err(fun->name, src, salign, c, len);
+			ERR("%s(align %d, %d, %d) failed\n", fun->name, salign, c, len);
+			quoteat("got", src, len+A, i);
 			return;
 		}
 	}
-	for (; i < len%A; i++) {
-		if (src[i] != '*') {
-			err(fun->name, src, salign, c, len);
+	for (; i < len+A; i++) {
+		if (src[i] != '?') {
+			ERR("%s(align %d, %d, %d) failed\n", fun->name, salign, c, len);
+			quoteat("got", src, len+A, i);
 			return;
 		}
 	}
@@ -89,7 +84,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int s = 0; s < A; s++) {
 			int n;
 			for (n = 0; n < 100; n++) {
@@ -103,8 +98,8 @@ int main()
 				test(funtab+i, s, 0xaa25, n);
 			}
 		}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/stpcpy.c b/string/test/stpcpy.c
index 9050227..9001057 100644
--- a/string/test/stpcpy.c
+++ b/string/test/stpcpy.c
@@ -11,6 +11,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -29,14 +30,11 @@ F(__stpcpy_aarch64_sve)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
-static char dbuf[LEN+2*A];
-static char sbuf[LEN+2*A];
-static char wbuf[LEN+2*A];
+static char dbuf[LEN+2*A+1];
+static char sbuf[LEN+2*A+1];
+static char wbuf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
@@ -54,6 +52,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	void *p;
 	int i;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || dalign >= A || salign >= A)
 		abort();
 	for (i = 0; i < len+A; i++) {
@@ -62,7 +62,7 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	}
 	for (i = 0; i < len; i++)
 		s[i] = w[i] = 'a' + i%23;
-	s[i] = w[i] = '\0';
+	s[len] = w[len] = '\0';
 
 	p = fun->fun(d, s);
 	if (p != d + len)
@@ -70,8 +70,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	for (i = 0; i < len+A; i++) {
 		if (dst[i] != want[i]) {
 			ERR("%s(align %d, align %d, %d) failed\n", fun->name, dalign, salign, len);
-			ERR("got : %.*s\n", dalign+len+1, dst);
-			ERR("want: %.*s\n", dalign+len+1, want);
+			quoteat("got", dst, len+A, i);
+			quoteat("want", want, len+A, i);
 			break;
 		}
 	}
@@ -81,7 +81,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int d = 0; d < A; d++)
 			for (int s = 0; s < A; s++) {
 				int n;
@@ -90,8 +90,8 @@ int main()
 				for (; n < LEN; n *= 2)
 					test(funtab+i, d, s, n);
 			}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/strchr.c b/string/test/strchr.c
index 80a454a..d6ed39a 100644
--- a/string/test/strchr.c
+++ b/string/test/strchr.c
@@ -11,6 +11,7 @@
 #include <string.h>
 #include <limits.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -30,13 +31,10 @@ F(__strchr_aarch64_sve)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define SP 512
 #define LEN 250000
-static char sbuf[LEN+2*A];
+static char sbuf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
@@ -51,24 +49,27 @@ static void test(const struct fun *fun, int align, int seekpos, int len)
 	int seekchar = 0x1;
 	void *p;
 
-	if (len > LEN || seekpos >= len - 1 || align >= A)
+	if (err_count >= ERR_LIMIT)
+		return;
+	if (len > LEN || seekpos >= len || align >= A)
 		abort();
 	if (seekchar >= 'a' && seekchar <= 'a' + 23)
 		abort();
 
 	for (int i = 0; i < len + A; i++)
 		src[i] = '?';
-	for (int i = 0; i < len - 2; i++)
+	for (int i = 0; i < len; i++)
 		s[i] = 'a' + i%23;
 	if (seekpos != -1)
 		s[seekpos] = seekchar;
-	s[len - 1] = '\0';
+	s[len] = '\0';
 
 	p = fun->fun(s, seekchar);
 
 	if (p != f) {
 		ERR("%s(%p,0x%02x,%d) returned %p\n", fun->name, s, seekchar, len, p);
-		ERR("expected: %p\n", f);
+		quoteat("input", s, len+A, seekpos);
+		printf("expected: %p\n", f);
 		abort();
 	}
 }
@@ -77,7 +78,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int a = 0; a < A; a++) {
 			int n;
 			for (n = 1; n < 100; n++) {
@@ -90,8 +91,8 @@ int main()
 				test(funtab+i, a, n / 2, n);
 			}
 		}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/strchrnul.c b/string/test/strchrnul.c
index 4e3f681..78192c4 100644
--- a/string/test/strchrnul.c
+++ b/string/test/strchrnul.c
@@ -13,6 +13,7 @@
 #include <string.h>
 #include <limits.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -32,13 +33,10 @@ F(__strchrnul_aarch64_sve)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define SP 512
 #define LEN 250000
-static char sbuf[LEN+2*A];
+static char sbuf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
@@ -49,29 +47,31 @@ static void test(const struct fun *fun, int align, int seekpos, int len)
 {
 	char *src = alignup(sbuf);
 	char *s = src + align;
-	char *f = seekpos != -1 ? s + seekpos : s + len - 1;
+	char *f = seekpos != -1 ? s + seekpos : s + len;
 	int seekchar = 0x1;
 	void *p;
 
-	if (len > LEN || seekpos >= len - 1 || align >= A)
+	if (err_count >= ERR_LIMIT)
+		return;
+	if (len > LEN || seekpos >= len || align >= A)
 		abort();
 	if (seekchar >= 'a' && seekchar <= 'a' + 23)
 		abort();
 
 	for (int i = 0; i < len + A; i++)
 		src[i] = '?';
-	for (int i = 0; i < len - 2; i++)
+	for (int i = 0; i < len; i++)
 		s[i] = 'a' + i%23;
 	if (seekpos != -1)
 		s[seekpos] = seekchar;
-	s[len - 1] = '\0';
+	s[len] = '\0';
 
 	p = fun->fun(s, seekchar);
 
 	if (p != f) {
 		ERR("%s(%p,0x%02x,%d) returned %p\n", fun->name, s, seekchar, len, p);
-		ERR("expected: %p\n", f);
-		abort();
+		quoteat("input", s, len+A, seekpos);
+		printf("expected: %p\n", f);
 	}
 }
 
@@ -79,7 +79,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int a = 0; a < A; a++) {
 			int n;
 			for (n = 1; n < 100; n++) {
@@ -92,8 +92,8 @@ int main()
 				test(funtab+i, a, n / 2, n);
 			}
 		}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/strcmp.c b/string/test/strcmp.c
index 91fa9dd..32f4c2a 100644
--- a/string/test/strcmp.c
+++ b/string/test/strcmp.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -34,20 +35,17 @@ F(__strcmp_armv6m)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
-static char s1buf[LEN+2*A];
-static char s2buf[LEN+2*A];
+static char s1buf[LEN+2*A+1];
+static char s2buf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
 	return (void*)(((uintptr_t)p + A-1) & -A);
 }
 
-static void test(const struct fun *fun, int s1align, int s2align, int len, int diffpos)
+static void test(const struct fun *fun, int s1align, int s2align, int len, int diffpos, int delta)
 {
 	char *src1 = alignup(s1buf);
 	char *src2 = alignup(s2buf);
@@ -55,26 +53,30 @@ static void test(const struct fun *fun, int s1align, int s2align, int len, int d
 	char *s2 = src2 + s2align;
 	int r;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || s1align >= A || s2align >= A)
 		abort();
-	if (diffpos > 1 && diffpos >= len-1)
+	if (diffpos >= len)
+		abort();
+	if ((diffpos < 0) != (delta == 0))
 		abort();
 
 	for (int i = 0; i < len+A; i++)
 		src1[i] = src2[i] = '?';
-	for (int i = 0; i < len-1; i++)
+	for (int i = 0; i < len; i++)
 		s1[i] = s2[i] = 'a' + i%23;
-	if (diffpos > 1)
-		s1[diffpos]++;
+	if (delta)
+		s1[diffpos] += delta;
 	s1[len] = s2[len] = '\0';
 
 	r = fun->fun(s1, s2);
 
-	if (((diffpos <= 1) && r != 0) || (diffpos > 1 && r == 0)) {
+	if ((delta == 0 && r != 0) || (delta > 0 && r <= 0) || (delta < 0 && r >= 0)) {
 		ERR("%s(align %d, align %d, %d) failed, returned %d\n",
 			fun->name, s1align, s2align, len, r);
-		ERR("src1: %.*s\n", s1align+len+1, src1);
-		ERR("src2: %.*s\n", s2align+len+1, src2);
+		quoteat("src1", src1, len+A, diffpos);
+		quoteat("src2", src2, len+A, diffpos);
 	}
 }
 
@@ -82,21 +84,26 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int d = 0; d < A; d++)
 			for (int s = 0; s < A; s++) {
 				int n;
-				for (n = 0; n < 100; n++) {
-					test(funtab+i, d, s, n, 0);
-					test(funtab+i, d, s, n, n / 2);
+				test(funtab+i, d, s, 0, -1, 0);
+				test(funtab+i, d, s, 1, -1, 0);
+				test(funtab+i, d, s, 1,  0, 1);
+				test(funtab+i, d, s, 1,  0, -1);
+				for (n = 2; n < 100; n++) {
+					test(funtab+i, d, s, n, -1, 0);
+					test(funtab+i, d, s, n, n - 1, -1);
+					test(funtab+i, d, s, n, n / 2, 1);
 				}
 				for (; n < LEN; n *= 2) {
-					test(funtab+i, d, s, n, 0);
-					test(funtab+i, d, s, n, n / 2);
+					test(funtab+i, d, s, n, -1, 0);
+					test(funtab+i, d, s, n, n / 2, -1);
 				}
 			}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/strcpy.c b/string/test/strcpy.c
index ea74c9e..68fc76f 100644
--- a/string/test/strcpy.c
+++ b/string/test/strcpy.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -30,14 +31,11 @@ F(__strcpy_arm)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
-static char dbuf[LEN+2*A];
-static char sbuf[LEN+2*A];
-static char wbuf[LEN+2*A];
+static char dbuf[LEN+2*A+1];
+static char sbuf[LEN+2*A+1];
+static char wbuf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
@@ -55,6 +53,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	void *p;
 	int i;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || dalign >= A || salign >= A)
 		abort();
 	for (i = 0; i < len+A; i++) {
@@ -63,7 +63,7 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	}
 	for (i = 0; i < len; i++)
 		s[i] = w[i] = 'a' + i%23;
-	s[i] = w[i] = '\0';
+	s[len] = w[len] = '\0';
 
 	p = fun->fun(d, s);
 	if (p != d)
@@ -71,8 +71,8 @@ static void test(const struct fun *fun, int dalign, int salign, int len)
 	for (i = 0; i < len+A; i++) {
 		if (dst[i] != want[i]) {
 			ERR("%s(align %d, align %d, %d) failed\n", fun->name, dalign, salign, len);
-			ERR("got : %.*s\n", dalign+len+1, dst);
-			ERR("want: %.*s\n", dalign+len+1, want);
+			quoteat("got", dst, len+A, i);
+			quoteat("want", want, len+A, i);
 			break;
 		}
 	}
@@ -82,7 +82,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int d = 0; d < A; d++)
 			for (int s = 0; s < A; s++) {
 				int n;
@@ -91,8 +91,8 @@ int main()
 				for (; n < LEN; n *= 2)
 					test(funtab+i, d, s, n);
 			}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/stringtest.h b/string/test/stringtest.h
new file mode 100644
index 0000000..b9c034a
--- /dev/null
+++ b/string/test/stringtest.h
@@ -0,0 +1,50 @@
+/*
+ * Common string test code.
+ *
+ * Copyright (c) 2020, Arm Limited.
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+
+/* Accounting errors for a test case.  */
+static int err_count;
+#define ERR_LIMIT 10
+#define ERR(...) (err_count++, printf(__VA_ARGS__))
+
+static inline void quotechar(unsigned char c)
+{
+	if (isprint(c))
+		putchar(c);
+	else
+		printf("\\x%02x", c);
+}
+
+/* quoted print around at or the entire string if at < 0.  */
+static void quoteat(const char *prefix, const void *p, int len, int at)
+{
+	static const int CTXLEN = 15;
+	int i;
+	const char *pre="\"";
+	const char *post="\"";
+	const char *s = p;
+	if (at > CTXLEN) {
+		s += at - CTXLEN;
+		len -= at - CTXLEN;
+		pre = "...\"";
+	}
+	if (at >= 0 && len > 2*CTXLEN + 1) {
+		len = 2*CTXLEN + 1;
+		post = "\"...";
+	}
+	printf("%4s: %s", prefix, pre);
+	for (i = 0; i < len; i++)
+		quotechar(s[i]);
+	printf("%s\n", post);
+}
+
+static inline void quote(const char *prefix, const void *p, int len)
+{
+	quoteat(prefix, p, len, -1);
+}
diff --git a/string/test/strlen.c b/string/test/strlen.c
index 96e6cd6..b2e2ffa 100644
--- a/string/test/strlen.c
+++ b/string/test/strlen.c
@@ -11,6 +11,7 @@
 #include <string.h>
 #include <limits.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -34,13 +35,10 @@ F(__strlen_armv6t2)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define SP 512
 #define LEN 250000
-static char sbuf[LEN+2*A];
+static char sbuf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
@@ -53,21 +51,22 @@ static void test(const struct fun *fun, int align, int len)
 	char *s = src + align;
 	size_t r;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || align >= A)
 		abort();
 
 	for (int i = 0; i < len + A; i++)
 		src[i] = '?';
-	for (int i = 0; i < len - 2; i++)
+	for (int i = 0; i < len; i++)
 		s[i] = 'a' + i%23;
-	s[len - 1] = '\0';
+	s[len] = '\0';
 
 	r = fun->fun(s);
-	if (r != len-1) {
+	if (r != len) {
 		ERR("%s(%p) returned %zu\n", fun->name, s, r);
-		ERR("input:    %.*s\n", align+len+1, src);
-		ERR("expected: %d\n", len);
-		abort();
+		quote("input", src, len);
+		printf("expected: %d\n", len);
 	}
 }
 
@@ -75,7 +74,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int a = 0; a < A; a++) {
 			int n;
 			for (n = 1; n < 100; n++)
@@ -83,8 +82,8 @@ int main()
 			for (; n < LEN; n *= 2)
 				test(funtab+i, a, n);
 		}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/strncmp.c b/string/test/strncmp.c
index 43f941d..fea4d01 100644
--- a/string/test/strncmp.c
+++ b/string/test/strncmp.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -28,20 +29,17 @@ F(__strncmp_aarch64_sve)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define LEN 250000
-static char s1buf[LEN+2*A];
-static char s2buf[LEN+2*A];
+static char s1buf[LEN+2*A+1];
+static char s2buf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
 	return (void*)(((uintptr_t)p + A-1) & -A);
 }
 
-static void test(const struct fun *fun, int s1align, int s2align, int maxlen, int diffpos, int len)
+static void test(const struct fun *fun, int s1align, int s2align, int maxlen, int diffpos, int len, int delta)
 {
 	char *src1 = alignup(s1buf);
 	char *src2 = alignup(s2buf);
@@ -49,28 +47,34 @@ static void test(const struct fun *fun, int s1align, int s2align, int maxlen, in
 	char *s2 = src2 + s2align;
 	int r;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || s1align >= A || s2align >= A)
 		abort();
-	if (diffpos > 1 && diffpos >= len-1)
+	if (diffpos >= len)
+		abort();
+	if ((diffpos < 0) != (delta == 0))
 		abort();
 
 	for (int i = 0; i < len+A; i++)
 		src1[i] = src2[i] = '?';
-	for (int i = 0; i < len-1; i++)
+	for (int i = 0; i < len; i++)
 		s1[i] = s2[i] = 'a' + i%23;
-	if (diffpos > 1)
-		s1[diffpos]++;
+	if (delta)
+		s1[diffpos] += delta;
 	s1[len] = s2[len] = '\0';
 
 	r = fun->fun(s1, s2, maxlen);
 
-	diffpos = maxlen <= diffpos ? 0 : diffpos;
-
-	if (((diffpos <= 1) && r != 0) || (diffpos > 1 && r == 0)) {
-		ERR("%s(align %d, align %d, %d (%d)) failed, returned %d (%d)\n",
-			fun->name, s1align, s2align, maxlen, len, r, diffpos);
-		ERR("src1: %.*s\n", s1align+len+1, src1);
-		ERR("src2: %.*s\n", s2align+len+1, src2);
+	if (diffpos >= maxlen) {
+		diffpos = -1;
+		delta = 0;
+	}
+	if ((delta == 0 && r != 0) || (delta > 0 && r <= 0) || (delta < 0 && r >= 0)) {
+		ERR("%s(align %d, align %d, %d) (len=%d, diffpos=%d) failed, returned %d\n",
+			fun->name, s1align, s2align, maxlen, len, diffpos, r);
+		quoteat("src1", src1, len+A, diffpos);
+		quoteat("src2", src2, len+A, diffpos);
 	}
 }
 
@@ -78,25 +82,32 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int d = 0; d < A; d++)
 			for (int s = 0; s < A; s++) {
 				int n;
-				for (n = 0; n < 100; n++) {
-					test(funtab+i, d, s, n,   0,   n);
-					test(funtab+i, d, s, n,   n/2, n);
-					test(funtab+i, d, s, n/2, 0,   n);
-					test(funtab+i, d, s, n/2, n/2, n);
+				test(funtab+i, d, s, 0,   -1,  0, 0);
+				test(funtab+i, d, s, 1,   -1,  0, 0);
+				test(funtab+i, d, s, 0,   -1,  1, 0);
+				test(funtab+i, d, s, 1,   -1,  1, 0);
+				test(funtab+i, d, s, 2,   -1,  1, 0);
+				test(funtab+i, d, s, 1,    0,  1, 1);
+				test(funtab+i, d, s, 1,    0,  1, -1);
+				for (n = 2; n < 100; n++) {
+					test(funtab+i, d, s, n,   -1,  n, 0);
+					test(funtab+i, d, s, n,   n/2, n, 1);
+					test(funtab+i, d, s, n/2, -1,  n, 0);
+					test(funtab+i, d, s, n/2, n/2, n, -1);
 				}
 				for (; n < LEN; n *= 2) {
-					test(funtab+i, d, s, n,   0,   n);
-					test(funtab+i, d, s, n,   n/2, n);
-					test(funtab+i, d, s, n/2, 0,   n);
-					test(funtab+i, d, s, n/2, n/2, n);
+					test(funtab+i, d, s, n,   -1,  n, 0);
+					test(funtab+i, d, s, n,   n/2, n, -1);
+					test(funtab+i, d, s, n/2, -1,  n, 0);
+					test(funtab+i, d, s, n/2, n/2, n, 1);
 				}
 			}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/strnlen.c b/string/test/strnlen.c
index db41f2a..29f85a0 100644
--- a/string/test/strnlen.c
+++ b/string/test/strnlen.c
@@ -13,6 +13,7 @@
 #include <string.h>
 #include <limits.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -31,13 +32,10 @@ F(__strnlen_aarch64_sve)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define SP 512
 #define LEN 250000
-static char sbuf[LEN+2*A];
+static char sbuf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
@@ -49,23 +47,24 @@ static void test(const struct fun *fun, int align, int maxlen, int len)
 	char *src = alignup(sbuf);
 	char *s = src + align;
 	size_t r;
-	size_t e = maxlen < len ? maxlen : len - 1;
+	size_t e = maxlen < len ? maxlen : len;
 
+	if (err_count >= ERR_LIMIT)
+		return;
 	if (len > LEN || align >= A)
 		abort();
 
 	for (int i = 0; i < len + A; i++)
 		src[i] = '?';
-	for (int i = 0; i < len - 2; i++)
+	for (int i = 0; i < len; i++)
 		s[i] = 'a' + i%23;
-	s[len - 1] = '\0';
+	s[len] = '\0';
 
 	r = fun->fun(s, maxlen);
 	if (r != e) {
-		ERR("%s(%p) returned %zu\n", fun->name, s, r);
-		ERR("input:    %.*s\n", align+len+1, src);
-		ERR("expected: %d\n", len);
-		abort();
+		ERR("%s(%p, %d) returned %zu\n", fun->name, s, maxlen, r);
+		quote("input", src, len+A);
+		printf("expected: %zu\n", e);
 	}
 }
 
@@ -73,7 +72,7 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int a = 0; a < A; a++) {
 			int n;
 			for (n = 1; n < 100; n++)
@@ -85,8 +84,8 @@ int main()
 				test(funtab+i, a, n/2, n);
 			}
 		}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;
diff --git a/string/test/strrchr.c b/string/test/strrchr.c
index 532fa51..d3d0bc5 100644
--- a/string/test/strrchr.c
+++ b/string/test/strrchr.c
@@ -11,6 +11,7 @@
 #include <string.h>
 #include <limits.h>
 #include "stringlib.h"
+#include "stringtest.h"
 
 static const struct fun
 {
@@ -29,13 +30,10 @@ F(__strrchr_aarch64_sve)
 	{0, 0}
 };
 
-static int test_status;
-#define ERR(...) (test_status=1, printf(__VA_ARGS__))
-
 #define A 32
 #define SP 512
 #define LEN 250000
-static char sbuf[LEN+2*A];
+static char sbuf[LEN+2*A+1];
 
 static void *alignup(void *p)
 {
@@ -50,25 +48,27 @@ static void test(const struct fun *fun, int align, int seekpos, int len)
 	int seekchar = 0x1;
 	void *p;
 
-	if (len > LEN || seekpos >= len - 1 || align >= A)
+	if (err_count >= ERR_LIMIT)
+		return;
+	if (len > LEN || seekpos >= len || align >= A)
 		abort();
 	if (seekchar >= 'a' && seekchar <= 'a' + 23)
 		abort();
 
 	for (int i = 0; i < len + A; i++)
 		src[i] = '?';
-	for (int i = 0; i < len - 2; i++)
+	for (int i = 0; i < len; i++)
 		s[i] = 'a' + i%23;
 	if (seekpos != -1)
 		s[seekpos/2] = s[seekpos] = seekchar;
-	s[len - 1] = '\0';
+	s[len] = '\0';
 
 	p = fun->fun(s, seekchar);
 
 	if (p != f) {
 		ERR("%s(%p,0x%02x,%d) returned %p\n", fun->name, s, seekchar, len, p);
-		ERR("expected: %p\n", f);
-		abort();
+		quote("input", s, len);
+		printf("expected: %p\n", f);
 	}
 }
 
@@ -76,11 +76,11 @@ int main()
 {
 	int r = 0;
 	for (int i=0; funtab[i].name; i++) {
-		test_status = 0;
+		err_count = 0;
 		for (int a = 0; a < A; a++) {
 			int n;
 			for (n = 1; n < 100; n++) {
-				for (int sp = 0; sp < n - 1; sp++)
+				for (int sp = 0; sp < n; sp++)
 					test(funtab+i, a, sp, n);
 				test(funtab+i, a, -1, n);
 			}
@@ -89,8 +89,8 @@ int main()
 				test(funtab+i, a, n / 2, n);
 			}
 		}
-		printf("%s %s\n", test_status ? "FAIL" : "PASS", funtab[i].name);
-		if (test_status)
+		printf("%s %s\n", err_count ? "FAIL" : "PASS", funtab[i].name);
+		if (err_count)
 			r = -1;
 	}
 	return r;