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-Wstring-compare in tools/perf/ #900

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nickdesaulniers opened this issue Feb 23, 2020 · 3 comments
Closed

-Wstring-compare in tools/perf/ #900

nickdesaulniers opened this issue Feb 23, 2020 · 3 comments
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-Wstring-compare [BUG] linux A bug that should be fixed in the mainline kernel. [FIXED][LINUX] 5.6 This bug was fixed in Linux 5.6

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@nickdesaulniers
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nickdesaulniers commented Feb 23, 2020 •
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$ make CC=clang tools/perf
builtin-diff.c:1315:18: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                        ^  ~~~~~~~~~~~~~~~
builtin-diff.c:1315:51: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                         ^  ~~~~~~~~~~~~~~~
2 errors generated.
util/block-info.c:298:18: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                        ^  ~~~~~~~~~~~~~~~
util/block-info.c:298:51: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                         ^  ~~~~~~~~~~~~~~~
2 errors generated.
util/map.c:434:15: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
                if (srcline != SRCLINE_UNKNOWN)
                            ^  ~~~~~~~~~~~~~~~
1 error generated.
@nickdesaulniers nickdesaulniers added the [BUG] linux A bug that should be fixed in the mainline kernel. label Feb 23, 2020
fengguang pushed a commit to 0day-ci/linux that referenced this issue Feb 23, 2020
@nickdesaulniers @intel-lab-lkp
perf: fix -Wstring-compare
a9b799a 
Clang warns:

util/block-info.c:298:18: error: result of comparison against a string
literal is unspecified (use an explicit string comparison function
instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                        ^  ~~~~~~~~~~~~~~~
util/block-info.c:298:51: error: result of comparison against a string
literal is unspecified (use an explicit string comparison function
instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                         ^  ~~~~~~~~~~~~~~~
util/block-info.c:298:18: error: result of comparison against a string
literal is unspecified (use an explicit string
comparison function instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                        ^  ~~~~~~~~~~~~~~~
util/block-info.c:298:51: error: result of comparison against a string
literal is unspecified (use an explicit string comparison function
instead) [-Werror,-Wstring-compare]
        if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                         ^  ~~~~~~~~~~~~~~~
util/map.c:434:15: error: result of comparison against a string literal
is unspecified (use an explicit string comparison function instead)
[-Werror,-Wstring-compare]
                if (srcline != SRCLINE_UNKNOWN)
                            ^  ~~~~~~~~~~~~~~~

Link: ClangBuiltLinux#900
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
@nickdesaulniers nickdesaulniers added the [PATCH] Submitted A patch has been submitted for review label Feb 23, 2020
@nickdesaulniers
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https://lore.kernel.org/lkml/20200223193456.25291-1-nick.desaulniers@gmail.com/T/#u

@nickdesaulniers nickdesaulniers changed the title make CC=clang tools/perf fails -Wstring-compare in tools/perf/ Feb 23, 2020
@nickdesaulniers nickdesaulniers added [PATCH] Accepted A submitted patch has been accepted upstream and removed [PATCH] Submitted A patch has been submitted for review labels Mar 6, 2020
@nickdesaulniers
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https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=perf/urgent&id=cfd3bc752a3f5529506d279deb42e3bc8055695b

@nathanchance
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Merged into mainline: https://git.kernel.org/linus/cfd3bc752a3f5529506d279deb42e3bc8055695b

@nathanchance nathanchance added [FIXED][LINUX] 5.6 This bug was fixed in Linux 5.6 and removed [PATCH] Accepted A submitted patch has been accepted upstream labels Mar 16, 2020
fengguang pushed a commit to 0day-ci/linux that referenced this issue Mar 19, 2020
@nickdesaulniers @acmel
perf diff: Fix undefined string comparison spotted by clang's -Wstrin…
c395c35 
…g-compare

clang warns:

  util/block-info.c:298:18: error: result of comparison against a string
  literal is unspecified (use an explicit string comparison function
  instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                          ^  ~~~~~~~~~~~~~~~
  util/block-info.c:298:51: error: result of comparison against a string
  literal is unspecified (use an explicit string comparison function
  instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                           ^  ~~~~~~~~~~~~~~~
  util/block-info.c:298:18: error: result of comparison against a string
  literal is unspecified (use an explicit string
  comparison function instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                          ^  ~~~~~~~~~~~~~~~
  util/block-info.c:298:51: error: result of comparison against a string
  literal is unspecified (use an explicit string comparison function
  instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                           ^  ~~~~~~~~~~~~~~~
  util/map.c:434:15: error: result of comparison against a string literal
  is unspecified (use an explicit string comparison function instead)
  [-Werror,-Wstring-compare]
                  if (srcline != SRCLINE_UNKNOWN)
                              ^  ~~~~~~~~~~~~~~~

Reviewer Notes:

Looks good to me. Some more context:
https://clang.llvm.org/docs/DiagnosticsReference.html#wstring-compare
The spec says:
J.1 Unspecified behavior
The following are unspecified:
.. Whether two string literals result in distinct arrays (6.4.5).

Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Keeping <john@metanate.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: clang-built-linux@googlegroups.com
Link: ClangBuiltLinux#900
Link: http://lore.kernel.org/lkml/20200223193456.25291-1-nick.desaulniers@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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-Wstring-compare [BUG] linux A bug that should be fixed in the mainline kernel. [FIXED][LINUX] 5.6 This bug was fixed in Linux 5.6
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