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86c2982568
This refreshes the line numbers, removes any fuzz (which would make any future forward ports easier) and standardizes the patch/file headers (which makes them easier to read). Signed-off-by: Alexey Neyman <stilor@att.net>
71 lines
2.0 KiB
Diff
71 lines
2.0 KiB
Diff
From 9df2d784439720abbf67fa96c6515a5c4a9f230a Mon Sep 17 00:00:00 2001
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From: Keith Packard <keithp@keithp.com>
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Date: Thu, 14 Jan 2021 18:48:44 -0800
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Subject: [PATCH 2/2] tinystdio: Fix snprintf(buf, 0, ...) to not smash buffer
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snprintf(buf, 0) should not write anything to the destination, not
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even a trailing '\0'. The tinystdio implementation had a signed
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comparison bug where this case would cause a null to be placed in the
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output buffer at the size of the data that would have been written.
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Add a test to make sure snprintf respects the 'len' parameter
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correctly.
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Signed-off-by: Keith Packard <keithp@keithp.com>
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---
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newlib/libc/tinystdio/snprintf.c | 2 +-
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test/printf_scanf.c | 31 +++++++++++++++++++++++++++++++
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2 files changed, 32 insertions(+), 1 deletion(-)
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--- a/newlib/libc/tinystdio/snprintf.c
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+++ b/newlib/libc/tinystdio/snprintf.c
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@@ -56,7 +56,7 @@
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i = vfprintf(&f.file, fmt, ap);
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va_end(ap);
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- if (n >= 0 && i >= 0)
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+ if ((int) n >= 0 && i >= 0)
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s[i < n ? i : n] = 0;
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return i;
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--- a/test/printf_scanf.c
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+++ b/test/printf_scanf.c
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@@ -96,6 +96,37 @@
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fflush(stdout);
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}
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#endif
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+
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+ /*
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+ * test snprintf to make sure it doesn't overwrite the specified buffer
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+ * length (even if that is zero)
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+ */
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+ for (x = 0; x <= 6; x++) {
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+ char tbuf[10] = "xxxxxxxxx";
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+ const char ref[10] = "xxxxxxxxx";
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+ int i = snprintf(tbuf, x, "%s", "123");
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+ int y = x <= 4 ? x : 4;
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+ if (i != 3) {
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+ printf("snprintf(tbuf, %d, \"%%s\", \"123\") return %d instead of %d\n",
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+ x, i, 3);
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+ errors++;
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+ }
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+ int l = strlen(tbuf);
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+ if (y > 0 && l != y - 1) {
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+ printf("returned buffer len want %d got %d\n", y - 1, l);
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+ errors++;
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+ }
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+ if (y > 0 && strncmp(tbuf, "123", y - 1) != 0) {
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+ strncpy(buf, "123", y - 1);
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+ buf[y-1] = '\0';
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+ printf("returned buffer want %s got %s\n", buf, tbuf);
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+ errors++;
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+ }
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+ if (memcmp(tbuf + y, ref + y, sizeof(tbuf) - y) != 0) {
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+ printf("tail of buf mangled %s\n", tbuf + y);
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+ errors++;
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+ }
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+ }
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for (x = 0; x < 32; x++) {
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unsigned int v = 0x12345678 >> x;
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unsigned int r;
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