It's not allowed to do a goto into an expression statement.
For example, it's not well defined what should happen if such
an expression is not otherwise reachable and/or can be optimized
away. For such situations GCC issues an error, clang doesn't
and produce a valid IR but Spare produce an invalid IR with
branches to unexisting BBs.
The goals of the patches in this series are:
*) to detect such gotos at evaluation time;
*) issue a sensible error message;
*) avoid the linearization of functions with invalid gotos.
The implementation principle behind these is to add a new kind
of scope (label_scope), one for the usual function scope of
labels one for each statement expressions. This new scope,
instead of being used as a real scope for the visibility of
labels, is used to mark where labels are defined and where
they're used.
Using this label scope as a real scope controling the
visibility of labels was quite appealing and was the initial
drive for this implementation but has the problem of inner
scope shadowing earlier occurence of labels identically
named. This is of course desired for 'normal' symbols but for
labels (which are normally visible in the whole function
and which may be used before being declared/defined)
it has the disadvantage of:
*) inhibiting the detecting of misuses once an inner scope
is closed
*) allowing several distinct labels with the same name
in a single function (this can be regarded as a feature
but __label__ at block scope should be used for this)
*) create diffrences about what is permssble or not between
sparse and GCC or clang.
Changes since v1:
* move most of the checks from eveluation time to parsing time
* add warnings for unused labels based on code from Linus
* add support for label attributes 'unused'
* add to label-expressions the same kind of checks than
those done for gotos
* use the correct position in warnings
* lots of small improvements
Luc Van Oostenryck (28):
misc: fix testcase typeof-safe
misc: s/fntype/rettype/
misc: always use the node for current_fn
bad-goto: add testcase for 'jump inside discarded expression statement'
bad-goto: add testcases for linearization of invalid labels
bad-goto: reorganize testcases and add some more
bad-goto: do not linearize if the IR will be invalid
bad-goto: reorg test in evaluate_goto_statement()
bad-goto: simplify testing of undeclared labels
bad-goto: do not linearize function with undeclared labels
bad-goto: catch labels with reserved names
scope: no memset() needed after __alloc_scope()
scope: move scope opening/ending inside compound_statement()
scope: extract bind_symbol_with_scope() from bind_symbol()
scope: __func__ is special
scope: __label__ is special
scope: s/{start,end}_symbol_scope/{start,end}_block_scope/
scope: make function_scope invalid outside functions
scope: let labels have their own scope
scope: add is_in_scope()
scope: give a scope for labels & gotos
bad-goto: jumping inside a statemet expression is an error
bad-goto: label expression inside a statement expression is UB
bad-goto: extract check_label_declaration()
bad-goto: check declaration of label expressions
bad-label: check for unused labels
bad-label: mark labels as used when needed
bad-label: respect attribute((unused))
evaluate.c | 36 ++++++--
expand.c | 2 +-
expression.c | 12 +--
linearize.c | 2 +-
parse.c | 73 +++++++++++++----
parse.h | 4 +-
scope.c | 46 +++++++++--
scope.h | 10 ++-
symbol.c | 13 ++-
symbol.h | 7 ++
validation/__func__-scope.c | 8 ++
.../{asm-goto-lables.c => asm-goto-labels.c} | 0
validation/label-asm.c | 1 +
validation/label-attr.c | 2 +-
validation/label-scope-cgoto.c | 82 +++++++++++++++++++
validation/label-scope.c | 5 +-
validation/label-scope1.c | 42 ++++++++++
validation/label-scope2.c | 31 +++++++
validation/label-stmt-expr0.c | 38 +++++++++
validation/label-stmt-expr1.c | 28 +++++++
validation/label-stmt-expr2.c | 46 +++++++++++
validation/label-unused.c | 29 +++++++
validation/linear/goto-invalid.c | 18 ++++
.../linear/goto-stmt-expr-conditional.c | 27 ++++++
.../linear/goto-stmt-expr-short-circuit.c | 31 +++++++
validation/linear/label-scope-cgoto.c | 10 +++
.../label-stmt-dropped.c} | 4 +-
.../label-stmt-expr0.c} | 4 +-
...reachable-label0.c => label-unreachable.c} | 3 +-
validation/typeof-safe.c | 26 ++++--
30 files changed, 576 insertions(+), 64 deletions(-)
create mode 100644 validation/__func__-scope.c
rename validation/{asm-goto-lables.c => asm-goto-labels.c} (100%)
create mode 100644 validation/label-scope-cgoto.c
create mode 100644 validation/label-scope1.c
create mode 100644 validation/label-scope2.c
create mode 100644 validation/label-stmt-expr0.c
create mode 100644 validation/label-stmt-expr1.c
create mode 100644 validation/label-stmt-expr2.c
create mode 100644 validation/label-unused.c
create mode 100644 validation/linear/goto-invalid.c
create mode 100644 validation/linear/goto-stmt-expr-conditional.c
create mode 100644 validation/linear/goto-stmt-expr-short-circuit.c
create mode 100644 validation/linear/label-scope-cgoto.c
rename validation/{discarded-label-statement.c => linear/label-stmt-dropped.c} (84%)
rename validation/{label-expr.c => linear/label-stmt-expr0.c} (75%)
rename validation/linear/{unreachable-label0.c => label-unreachable.c} (80%)
base-commit: 146e6a63e715e0c3e08aacbcaa79ff8930289297
--
2.26.2
