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19468a623a
Currently ASSERT() prints the stringified condition and without macro expansions so simple constants like BTRFS_MAX_METADATA_BLOCKSIZE remain readable in the output. There are expressions where we'd like to see the exact values but all we get is something like: assertion failed: em->start <= start && start < extent_map_end(em), in fs/btrfs/extent_map.c:613 It would be nice to be able to print any additional information to help understand the problem. With some preprocessor magic and compile-time optimizations we can enhance ASSERT to work like that as well: ASSERT(value > limit, "value=%llu limit=%llu", value, limit); with free-form printk arguments that will be part of the assertion message. Pros: - helps debugging and understanding reported problems - the optional format is verified at compile-time Cons: - increases the .ko size - writing the assertion code is repetitive (condition, format, values) - format and variable type must match (extra lookup) - needs gcc 8.x and newer, otherwise it's the short format Recommended use is for non-trivial expressions, so basic ASSERT(value) can be used for pointers or sometimes integers. The format has been slightly updated to also print the result of the evaluation of the condition, appended to the stringified condition as "condition :: <value>". Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.