This adds a new warning, -Wglobal-constructors, that warns whenever a
decl requires a global constructor or destructor. This new warning fires
whenever a thread_local or global variable is declared whose type has a
non-trivial constructor or destructor. When faced with both a constructor
and a destructor, the error message mentions the destructor and is only
fired once.
This warning mirrors the Clang option -Wglobal-constructors, which warns
on the same thing. -Wglobal-constructors was present in Apple's GCC and
later made its way into Clang.
Bootstrapped and regression-tested on x86-64 linux, new tests passing.
gcc/ChangeLog:
2019-05-28 Sean Gillespie <s...@swgillespie.me>
* doc/invoke.texi: Add new flag -Wglobal-constructors.
gcc/c-family/ChangeLog:
2019-05-28 Sean Gillespie <s...@swgillespie.me>
* c.opt: Add new flag -Wglobal-constructors.
gcc/cp/ChangeLog:
2019-05-28 Sean Gillespie <s...@swgillespie.me>
* decl.c (expand_static_init): Warn if a thread local or static decl
requires a non-trivial constructor or destructor.
gcc/testsuite/ChangeLog:
2019-05-28 Sean Gillespie <s...@swgillespie.me>
* g++.dg/warn/global-constructors-1.C: New test.
* g++.dg/warn/global-constructors-2.C: New test.
---
gcc/c-family/c.opt | 4 +++
gcc/cp/decl.c | 17 ++++++++++---
gcc/doc/invoke.texi | 7 ++++++
.../g++.dg/warn/global-constructors-1.C | 25 +++++++++++++++++++
.../g++.dg/warn/global-constructors-2.C | 23 +++++++++++++++++
5 files changed, 73 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/global-constructors-1.C
create mode 100644 gcc/testsuite/g++.dg/warn/global-constructors-2.C
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 046d489f7eb..cf62625ca42 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -613,6 +613,10 @@ Wformat-truncation=
C ObjC C++ LTO ObjC++ Joined RejectNegative UInteger Var(warn_format_trunc)
Warning LangEnabledBy(C ObjC C++ LTO ObjC++,Wformat=, warn_format >= 1, 0)
IntegerRange(0, 2)
Warn about calls to snprintf and similar functions that truncate output.
+Wglobal-constructors
+C++ ObjC++ Var(warn_global_constructors) Warning
+Warn when a global declaration requires a constructor to initialize.
+
Wif-not-aligned
C ObjC C++ ObjC++ Var(warn_if_not_aligned) Init(1) Warning
Warn when the field in a struct is not aligned.
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 19d14a6a5e9..c1d66195bd7 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -8467,10 +8467,21 @@ expand_static_init (tree decl, tree init)
finish_then_clause (if_stmt);
finish_if_stmt (if_stmt);
}
- else if (CP_DECL_THREAD_LOCAL_P (decl))
- tls_aggregates = tree_cons (init, decl, tls_aggregates);
else
- static_aggregates = tree_cons (init, decl, static_aggregates);
+ {
+ if (CP_DECL_THREAD_LOCAL_P (decl))
+ tls_aggregates = tree_cons (init, decl, tls_aggregates);
+ else
+ static_aggregates = tree_cons (init, decl, static_aggregates);
+
+ if (warn_global_constructors)
+ {
+ if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (decl)))
+ warning(OPT_Wglobal_constructors, "declaration requires a global
destructor");
+ else
+ warning(OPT_Wglobal_constructors, "declaration requires a global
constructor");
+ }
+ }
}
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 4964cc41ba3..a9b2e47a302 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -312,6 +312,7 @@ Objective-C and Objective-C++ Dialects}.
-Wformat-security -Wformat-signedness -Wformat-truncation=@var{n} @gol
-Wformat-y2k -Wframe-address @gol
-Wframe-larger-than=@var{byte-size} -Wno-free-nonheap-object @gol
+-Wglobal-constructors @gol
-Wjump-misses-init @gol
-Whsa -Wif-not-aligned @gol
-Wignored-qualifiers -Wignored-attributes -Wincompatible-pointer-types @gol
@@ -6509,6 +6510,12 @@ to @option{-Wframe-larger-than=}@samp{SIZE_MAX} or
larger.
Do not warn when attempting to free an object that was not allocated
on the heap.
+@item -Wglobal-constructors @r{(C++ and Objective-C++ only)}
+@opindex Wglobal-constructors
+@opindex Wno-global-constructors
+Warn if the compiler detects a global declaration that requires
+a constructor to initialize.
+
@item -Wstack-usage=@var{byte-size}
@opindex Wstack-usage
@opindex Wno-stack-usage
diff --git a/gcc/testsuite/g++.dg/warn/global-constructors-1.C
b/gcc/testsuite/g++.dg/warn/global-constructors-1.C
new file mode 100644
index 00000000000..5a6869e9dcd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/global-constructors-1.C
@@ -0,0 +1,25 @@
+// { dg-do compile }
+// { dg-options "-Wglobal-constructors" }
+
+struct with_ctor {
+ int x;
+ with_ctor() : x(42) {}
+};
+
+struct with_dtor {
+ ~with_dtor() {}
+};
+
+struct with_both {
+ int x;
+ with_both() : x(42) {}
+ ~with_both() {}
+};
+
+with_ctor global_var; /* { dg-warning "declaration requires a global
constructor" } */
+with_dtor global_var2; /* { dg-warning "declaration requires a global
destructor" } */
+with_both global_var3; /* { dg-warning "declaration requires a global
destructor" } */
+
+int main() {
+ static with_ctor global_var; /* { dg-bogus "declaration requires a global
constructor" } */
+}
diff --git a/gcc/testsuite/g++.dg/warn/global-constructors-2.C
b/gcc/testsuite/g++.dg/warn/global-constructors-2.C
new file mode 100644
index 00000000000..e753b9cb507
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/global-constructors-2.C
@@ -0,0 +1,23 @@
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+// { dg-options "-Wglobal-constructors" }
+
+struct with_ctor {
+ int x;
+
+ with_ctor() : x(42) {}
+};
+
+struct with_dtor {
+ ~with_dtor() {}
+};
+
+struct with_both {
+ int x;
+ with_both() : x(42) {}
+ ~with_both() {}
+};
+
+thread_local with_ctor global_var; /* { dg-warning "declaration requires a
global constructor" } */
+thread_local with_dtor global_var2; /* { dg-warning "declaration requires a
global destructor" } */
+thread_local with_both global_var3; /* { dg-warning "declaration requires a
global destructor" } */
--
2.20.1
