73 lines
2.9 KiB
Diff
73 lines
2.9 KiB
Diff
commit ff1096a0c24c3a302a58864392270e6622e21a03
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Author: Paul Eggert <eggert@cs.ucla.edu>
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Date: Wed Jun 21 11:19:13 2023 -0700
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cmp: fix -s bug when comparing /proc files
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* NEWS: Mention this.
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* src/cmp.c (main, cmp): Do not trust st_size == 0, as it may
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be a /proc file.
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* tests/brief-vs-stat-zero-kernel-lies: Also test cmp -s.
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diff --git a/NEWS b/NEWS
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index 0b7cf48..00ee5b6 100644
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--- a/NEWS
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+++ b/NEWS
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@@ -10,6 +10,12 @@ GNU diffutils NEWS -*- outline -*-
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cmp/diff can again work with file dates past Y2K38
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[bug introduced in 3.9]
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+ cmp -s no longer mishandles /proc files, for which the Linux kernel
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+ reports a zero size even when nonempty. For example, the following
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+ shell command now outputs nothing, as it should:
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+ cp /proc/cmdline t; cmp -s /proc/cmdline t || echo files differ
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+ [bug present since "the beginning"]
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+
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diff -D no longer fails to output #ifndef lines.
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[bug#61193 introduced in 3.9]
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diff --git a/src/cmp.c b/src/cmp.c
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index 4bf0a4c..936125c 100644
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--- a/src/cmp.c
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+++ b/src/cmp.c
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@@ -338,13 +338,14 @@ main (int argc, char **argv)
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}
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/* If only a return code is needed,
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- and if both input descriptors are associated with plain files,
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+ and both input descriptors are associated with plain files,
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+ and the file sizes are nonzero so they are not Linux /proc files,
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conclude that the files differ if they have different sizes
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and if more bytes will be compared than are in the smaller file. */
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if (comparison_type == type_status
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- && 0 <= stat_buf[0].st_size && S_ISREG (stat_buf[0].st_mode)
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- && 0 <= stat_buf[1].st_size && S_ISREG (stat_buf[1].st_mode))
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+ && 0 < stat_buf[0].st_size && S_ISREG (stat_buf[0].st_mode)
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+ && 0 < stat_buf[1].st_size && S_ISREG (stat_buf[1].st_mode))
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{
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off_t s0 = stat_buf[0].st_size - file_position (0);
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off_t s1 = stat_buf[1].st_size - file_position (1);
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@@ -401,7 +402,7 @@ cmp (void)
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? bytes : TYPE_MAXIMUM (off_t));
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for (f = 0; f < 2; f++)
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- if (0 <= stat_buf[f].st_size && S_ISREG (stat_buf[f].st_mode))
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+ if (0 < stat_buf[f].st_size && S_ISREG (stat_buf[f].st_mode))
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{
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off_t file_bytes = stat_buf[f].st_size - file_position (f);
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if (file_bytes < byte_number_max)
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diff --git a/tests/brief-vs-stat-zero-kernel-lies b/tests/brief-vs-stat-zero-kernel-lies
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index 82b33e6..7cc2dc7 100755
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--- a/tests/brief-vs-stat-zero-kernel-lies
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+++ b/tests/brief-vs-stat-zero-kernel-lies
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@@ -35,4 +35,9 @@ printf 'diff\0--brief\0/proc/self/cmdline\0bin\0' > bin || framework_failure_
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diff --brief /proc/self/cmdline bin > out 2>&1 || fail=1
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compare /dev/null out || fail=1
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+# Similarly for cmp -s.
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+printf 'cmp\0-s\0/proc/self/cmdline\0bin\0' > bin || framework_failure_
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+cmp -s /proc/self/cmdline bin > out 2>&1 || fail=1
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+compare /dev/null out || fail=1
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+
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Exit $fail
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