I spend an increasing amount of my time looking at "Corrupted block detected"
failures in decompression. Not infrequently, I suspect that it is the result
of hardware failure, and that the blob has become bit-flipped or otherwise
corrupted somewhere along the line.
For that reason I was motivated to write a little tool to inspect blobs that
fail to decompress, to try modifying them, and then check whether they
decompress successfully. This seems like potentially a generally useful tool,
so I figured it might be worth putting in `contrib/`.
Test compilation performed with warnings. Author and license added. Test for failing grep on ancient OSX versions. Replaced the test image with something less noisy (which compresses better).
The test script combines the sources then builds and runs an example. A futher example is built if the Emscripten compiler is available on the system. Documentation covers building.
Compiling with clang-8 fails with the following errors:
largeNbDicts.c:562:37: error: implicit conversion turns floating-point
number into integer: 'const double' to 'U64' (aka 'unsigned long')
[-Werror,-Wfloat-conversion]
U64 const dTime_ns = result.nanoSecPerRun;
~~~~~~~~ ~~~~~~~^~~~~~~~~~~~~
zstdcli.c:300:5: error: '@return' command used in a comment that is
not attached to a function or method declaration
[-Werror,-Wdocumentation]
* @return 1 means that cover parameters were correct
~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
zstdcli.c:301:5: error: '@return' command used in a comment that is
not attached to a function or method declaration
[-Werror,-Wdocumentation]
* @return 0 in case of malformed parameters
~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
benchfn used to rely on mem.h, and util,
which in turn relied on platform.h.
Using benchfn outside of zstd required to bring all these dependencies.
Now, dependency is reduced to timefn only.
This required to create a separate timefn from util,
and rewrite benchfn and timefn to no longer need mem.h.
Separating timefn from util has a wide effect accross the code base,
as usage of time functions is widespread.
A lot of build scripts had to be updated to also include timefn.
as suggested in #1441.
generally U32 and unsigned are the same thing,
except when they are not ...
case : 32-bit compilation for MIPS (uint32_t == unsigned long)
A vast majority of transformation consists in transforming U32 into unsigned.
In rare cases, it's the other way around (typically for internal code, such as seeds).
Among a few issues this patches solves :
- some parameters were declared with type `unsigned` in *.h,
but with type `U32` in their implementation *.c .
- some parameters have type unsigned*,
but the caller user a pointer to U32 instead.
These fixes are useful.
However, the bulk of changes is about %u formating,
which requires unsigned type,
but generally receives U32 values instead,
often just for brevity (U32 is shorter than unsigned).
These changes are generally minor, or even annoying.
As a consequence, the amount of code changed is larger than I would expect for such a patch.
Testing is also a pain :
it requires manually modifying `mem.h`,
in order to lie about `U32`
and force it to be an `unsigned long` typically.
On a 64-bit system, this will break the equivalence unsigned == U32.
Unfortunately, it will also break a few static_assert(), controlling structure sizes.
So it also requires modifying `debug.h` to make `static_assert()` a noop.
And then reverting these changes.
So it's inconvenient, and as a consequence,
this property is currently not checked during CI tests.
Therefore, these problems can emerge again in the future.
I wonder if it is worth ensuring proper distinction of U32 != unsigned in CI tests.
It's another restriction for coding, adding more frustration during merge tests,
since most platforms don't need this distinction (hence contributor will not see it),
and while this can matter in theory, the number of platforms impacted seems minimal.
Thoughts ?
