Sparse improvements & regressions for Linux v5.9-rc1 -> v5.10-rc1

[Luc Van Oostenryck]

Hi,

Here is a comparison of Sparse's unique warnings between v5.9-rc1 &
v5.10-rc1 on x86-64 (defconfig + allyesconfig).

This time, there is a VERY significant decrease in the number of
warnings, almost 20% less. On ppc64, the difference is 31%. This big
difference is mainly but not only caused by "cast to restricted type"
warnings or related, like "different base types".

Some of these differences come from changes in Sparse, but most come
from changes in the kernel itself.

The raw logs as well as the result of the processing giving the
'unique warnings' are available at:
        git://github.com/lucvoo/sparse-logs.git


- 18621 14983 Total
+   191   210 Initializer entry defined twice
-   105    92 Using plain integer as NULL pointer
-   394     0 advancing past deep designator
      4     4 arithmetics on pointers to functions
+     0    88 array of flexible structures
-    12    10 bad assignment to restricted type
      4     4 cast between address spaces (__percpu -> __rcu)
-   261   257 cast from restricted type
-   473   468 cast removes address space '__iomem' of expression
      1     1 cast removes address space '__percpu' of expression
     15    15 cast removes address space '__rcu' of expression
-    43    20 cast removes address space '__user' of expression
-    13     0 cast to non-scalar
-  4550  2862 cast to restricted type
-   609   548 cast truncates bits from constant value
+   332   359 context imbalance - different lock contexts for basic block
+   467   472 context imbalance - unexpected unlock
+   189   191 context imbalance - wrong count at exit
-   109   106 dereference of noderef expression
+     0     1 division by zero
+     0     1 dubious one-bit signed bitfield
     16    16 dubious: !x & y
      1     1 dubious: !x | !y
      6     6 dubious: !x | y
     56    56 dubious: x & !y
-    20    19 dubious: x | !y
-     1     0 duplicate [noderef]
-    21    18 function with external linkage has definition
      2     2 implicit cast from nocast type
-   490   458 incompatible types in comparison expression (different address spaces)
+     3     4 incompatible types in comparison expression (different base types)
-     1     0 incompatible types in comparison expression (different type sizes)
      7     7 incompatible types in conditional expression (different base types)
-  1087  1031 incorrect type in argument (different address spaces)
-   494   477 incorrect type in argument (different base types)
-     1     0 incorrect type in argument (incompatible argument (different address spaces))
-   382   336 incorrect type in assignment (different address spaces)
-  4762  3513 incorrect type in assignment (different base types)
      1     1 incorrect type in assignment (different modifiers)
+   120   130 incorrect type in initializer (different address spaces)
-   131   124 incorrect type in initializer (different base types)
-     7     4 incorrect type in initializer (incompatible argument (different address spaces))
-    25    24 incorrect type in return expression (different address spaces)
-    30    25 incorrect type in return expression (different base types)
-   285   282 invalid assignment
     37    37 invalid bitfield specifier for type restricted type.
      7     7 invalid initializer
+     1     2 marked inline, but without a definition
-     1     0 memcpy with byte count of ...
-     5     4 memset with byte count of ...
      7     7 mixed bitwiseness
      8     8 mixing different enum types:
-     2     1 multiple address spaces given
     12    12 multiple definitions for ...
+     0     2 no generic selection for ...
-   918   902 restricted type degrades to integer
+     0     1 statement expected after label
+    12    16 static assertion failed
      5     5 subtraction of different types can't work (different address spaces)
     23    23 subtraction of functions? Share your drugs
      1     1 switch with no cases
+     0     1 symbol redeclared with different type (different address spaces)
-     5     2 symbol redeclared with different type (incompatible argument (different address spaces))
-  1852  1705 symbol was not declared. Should it be static?
      1     1 too long token expansion
      3     3 trying to concatenate long character string (8191 bytes max)