forked from wangliu-iscas/gcc-patch
-
Notifications
You must be signed in to change notification settings - Fork 3
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
c++: Check for indirect change of active union member in constexpr [P…
…R101631,PR102286] Ping for https://gcc.gnu.org/pipermail/gcc-patches/2023-September/631203.html Rebased on top of current trunk and bootstrap + regtest on x86_64-pc-linux-gnu now completed without errors. -- >8 -- This patch adds checks for attempting to change the active member of a union by methods other than a member access expression. To be able to properly distinguish `*(&u.a) = ` from `u.a = `, this patch redoes the solution for c++/59950 to avoid extranneous *&; it seems that the only case that needed the workaround was when copying empty classes. This patch also ensures that constructors for a union field mark that field as the active member before entering the call itself; this ensures that modifications of the field within the constructor's body don't cause false positives (as these will not appear to be member access expressions). This means that we no longer need to start the lifetime of empty union members after the constructor body completes. As a drive-by fix, this patch also ensures that value-initialised unions are considered to have activated their initial member for the purpose of checking stores, which catches some additional mistakes pre-C++20. PR c++/101631 PR c++/102286 gcc/cp/ChangeLog: * call.cc (build_over_call): Fold more indirect refs for trivial assignment op. * class.cc (type_has_non_deleted_trivial_default_ctor): Create. * constexpr.cc (cxx_eval_call_expression): Start lifetime of union member before entering constructor. (cxx_eval_store_expression): Activate member for value-initialised union. Check for accessing inactive union member indirectly. * cp-tree.h (type_has_non_deleted_trivial_default_ctor): Forward declare. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-89336-3.C: Fix union initialisation. * g++.dg/cpp1y/constexpr-union6.C: New test. * g++.dg/cpp2a/constexpr-union2.C: New test. * g++.dg/cpp2a/constexpr-union3.C: New test. * g++.dg/cpp2a/constexpr-union4.C: New test. * g++.dg/cpp2a/constexpr-union5.C: New test. * g++.dg/cpp2a/constexpr-union6.C: New test. Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
- Loading branch information
1 parent
c2d62cd
commit 965a5ae
Showing
11 changed files
with
345 additions
and
43 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,13 @@ | ||
| // { dg-do compile { target c++14 } } | ||
|
|
||
| union U { | ||
| int a; | ||
| float b; | ||
| }; | ||
|
|
||
| constexpr bool foo() { | ||
| U u {}; | ||
| u.b = 1.0f; // { dg-error "change of the active member" "" { target c++17_down } } | ||
| return u.b == 1.0f; | ||
| } | ||
| constexpr bool x = foo(); |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,30 @@ | ||
| // PR c++/101631 | ||
| // { dg-do compile { target c++20 } } | ||
|
|
||
| struct sso { | ||
| union { | ||
| int buf[10]; | ||
| int* alloc; | ||
| }; | ||
| }; | ||
|
|
||
| constexpr bool direct() { | ||
| sso val; | ||
| val.alloc = nullptr; | ||
| val.buf[5] = 42; | ||
| return true; | ||
| } | ||
| constexpr bool ok = direct(); | ||
|
|
||
|
|
||
| constexpr void perform_assignment(int& left, int right) noexcept { | ||
| left = right; // { dg-error "accessing .+ member instead of initialized" } | ||
| } | ||
|
|
||
| constexpr bool indirect() { | ||
| sso val; | ||
| val.alloc = nullptr; | ||
| perform_assignment(val.buf[5], 42); // { dg-message "in .constexpr. expansion" } | ||
| return true; | ||
| } | ||
| constexpr bool err = indirect(); // { dg-message "in .constexpr. expansion" } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,45 @@ | ||
| // { dg-do compile { target c++20 } } | ||
|
|
||
| struct S | ||
| { | ||
| union { | ||
| char buf[8]; | ||
| char* ptr; | ||
| }; | ||
| unsigned len; | ||
|
|
||
| constexpr S(const char* s, unsigned n) | ||
| { | ||
| char* p; | ||
| if (n > 7) | ||
| p = ptr = new char[n+1]; | ||
| else | ||
| p = buf; | ||
| for (len = 0; len < n; ++len) | ||
| p[len] = s[len]; // { dg-error "accessing uninitialized member" } | ||
| p[len] = '\0'; | ||
| } | ||
|
|
||
| constexpr ~S() | ||
| { | ||
| if (len > 7) | ||
| delete[] ptr; | ||
| } | ||
| }; | ||
|
|
||
| constexpr bool test1() | ||
| { | ||
| S s("test", 4); // { dg-message "in .constexpr. expansion" } | ||
| return true; | ||
| } | ||
|
|
||
| constexpr bool a = test1(); // { dg-message "in .constexpr. expansion" } | ||
|
|
||
|
|
||
| constexpr bool test2() | ||
| { | ||
| S s("hello world", 11); | ||
| return true; | ||
| } | ||
|
|
||
| constexpr bool b = test2(); |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,29 @@ | ||
| // { dg-do compile { target c++20 } } | ||
|
|
||
| // from [class.union.general] p5 | ||
|
|
||
| union A { int x; int y[4]; }; | ||
| struct B { A a; }; | ||
| union C { B b; int k; }; | ||
| constexpr int f() { | ||
| C c; // does not start lifetime of any union member | ||
| c.b.a.y[3] = 4; // OK, S(c.b.a.y[3]) contains c.b and c.b.a.y; | ||
| // creates objects to hold union members c.b and c.b.a.y | ||
| return c.b.a.y[3]; // OK, c.b.a.y refers to newly created object (see [basic.life]) | ||
| } | ||
| constexpr int a = f(); | ||
|
|
||
| struct X { const int a; int b; }; | ||
| union Y { X x; int k; };// { dg-message "does not implicitly begin its lifetime" } | ||
| constexpr int g() { | ||
| Y y = { { 1, 2 } }; // OK, y.x is active union member ([class.mem]) | ||
| int n = y.x.a; | ||
| y.k = 4; // OK, ends lifetime of y.x, y.k is active member of union | ||
|
|
||
| y.x.b = n; // { dg-error "accessing .* member instead of initialized .* member" } | ||
| // undefined behavior: y.x.b modified outside its lifetime, | ||
| // S(y.x.b) is empty because X's default constructor is deleted, | ||
| // so union member y.x's lifetime does not implicitly start | ||
| return 0; | ||
| } | ||
| constexpr int b = g(); // { dg-message "in .constexpr. expansion" } |
Oops, something went wrong.