2020
https://pmeerw.net/blog/programming/unused-return.html
2018
https://devblogs.microsoft.com/cppblog/exploring-clang-tooling-part-2-examining-the-clang-ast-with-clang-query/

#!/bin/sh
# unused-return.sh: Run clang-query to report unused return values.

# When --dump, print the AST of matching syntax.
if [ "x$1" = "x--dump" ]; then
  dump="set output dump"
  shift
fi

query='m
  callExpr(
    isExpansionInMainFile(),
    hasParent(anyOf(
      compoundStmt(),
      ifStmt(hasCondition(expr().bind("cond"))),
      whileStmt(hasCondition(expr().bind("cond"))),
      doStmt(hasCondition(expr().bind("cond")))
    )),
    unless(hasType(voidType())),
    unless(isTypeDependent()),
    unless(cxxOperatorCallExpr()),
    unless(callee(namedDecl(anyOf(
      hasName("memset"),
      hasName("setlength"),
      hasName("flags"),
      hasName("width"),
      hasName("__builtin_memcpy")
    )))),
    unless(equalsBoundNode("cond"))).bind("unused-return")'

clang-query-9 -extra-arg="-w" -c="set bind-root false" -c="$dump" -c="$query" "$@" --