[src/trunk]: src/usr.bin/xlint/lint1 lint: document limitations

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/8860da1e7584
branches:  trunk
changeset: 373646:8860da1e7584
user:      rillig <rillig%NetBSD.org@localhost>
date:      Wed Feb 22 23:55:05 2023 +0000

description:
lint: document limitations

diffstat:

 usr.bin/xlint/lint1/README.md |  15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diffs (29 lines):

diff -r f08f071e3f5a -r 8860da1e7584 usr.bin/xlint/lint1/README.md
--- a/usr.bin/xlint/lint1/README.md     Wed Feb 22 22:30:40 2023 +0000
+++ b/usr.bin/xlint/lint1/README.md     Wed Feb 22 23:55:05 2023 +0000
@@ -1,4 +1,4 @@
-[//]: # ($NetBSD: README.md,v 1.11 2023/02/05 13:06:36 rillig Exp $)
+[//]: # ($NetBSD: README.md,v 1.12 2023/02/22 23:55:05 rillig Exp $)
 
 # Introduction
 
@@ -64,6 +64,19 @@
 * The option `-q` enables additional queries that are not suitable as regular
   warnings but may be interesting to look at on a case-by-case basis.
 
+# Limitations
+
+Lint operates on the level of individual expressions.
+
+* It does not build an AST of the statements of a function, therefore it
+  cannot reliably analyze the control flow in a single function.
+* It does not store the control flow properties of functions, therefore it
+  cannot relate argument nullability with the return value.
+* It does not have information about functions, except for their prototypes,
+  therefore it cannot relate them across translation units.
+* It does not store detailed information about complex data types, therefore
+  it cannot cross-check them across translation units.
+
 # Fundamental types
 
 Lint mainly analyzes expressions (`tnode_t`), which are formed from operators