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Make toDelegate safe for function pointers #10599

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Dec 30, 2024
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Make toDelegate safe for function pointers #10599

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61 changes: 53 additions & 8 deletions std/functional.d
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Original file line number Diff line number Diff line change
Expand Up @@ -1814,6 +1814,13 @@ if (isCallable!(F))
{
return fp;
}
else static if (is(F Func == Func*) && is(Func == function))
{
return function(ref F fp) @trusted
{
return buildDelegate(fp);
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}(fp);
}
else static if (is(typeof(&F.opCall) == delegate)
|| (is(typeof(&F.opCall) V : V*) && is(V == function)))
{
Expand All @@ -1825,6 +1832,27 @@ if (isCallable!(F))
}
else
{
static assert(false, "Unsupported type of callable, please open an issue.");
}
}

///
@safe unittest
{
static int inc(ref uint num) {
num++;
return 8675309;
}

uint myNum = 0;
auto incMyNumDel = toDelegate(&inc);
auto returnVal = incMyNumDel(myNum);
assert(myNum == 1);
}

private template buildDelegate(F)
{
auto buildDelegate(auto ref F fp) {
alias DelType = typeof(&(new DelegateFaker!(F)).doIt);

static struct DelegateFields {
Expand Down Expand Up @@ -1854,21 +1882,22 @@ if (isCallable!(F))
}
}

///
@system unittest
@safe unittest
{
static int inc(ref uint num) {
num++;
return 8675309;
}

uint myNum = 0;
auto incMyNumDel = toDelegate(&inc);
auto returnVal = incMyNumDel(myNum);
assert(myNum == 1);
uint myNum = 0x1337;
struct S1 { int opCall() { inc(myNum); return myNum; } }
static assert(!is(typeof(&s1.opCall) == delegate));
S1 s1;
Comment on lines +1894 to +1895
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What’s that doing?
In static assert(!is(typeof(&s1.opCall) == delegate));, the local variable s1 isn’t in scope.
If you swap the lines, the static assert passes.

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good catch

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Apparently, it’s a copy&paste of this code:

phobos/std/functional.d

Lines 1891 to 1901 in 8c6fca9

struct S1 { int opCall() { inc(myNum); return myNum; } }
static assert(!is(typeof(&s1.opCall) == delegate));
S1 s1;
auto getvals1 = toDelegate(s1);
assert(getvals1() == 4);
struct S2 { static int opCall() { return 123456; } }
static assert(!is(typeof(&S2.opCall) == delegate));
S2 s2;
auto getvals2 =&S2.opCall;
assert(getvals2() == 123456);

https://github.com/dlang/phobos/blame/8c6fca9ccdb30b69b627808c698526a76f7c4248/std/functional.d#L1891-L1901

auto getvals1 = toDelegate(s1);
assert(getvals1() == 0x1338);
}

@system unittest // not @safe due to toDelegate
@system unittest
{
static int inc(ref uint num) {
num++;
Expand Down Expand Up @@ -1954,7 +1983,7 @@ if (isCallable!(F))
}


@system unittest
@safe unittest
{
static struct S1 { static void opCall()() { } }
static struct S2 { static T opCall(T = int)(T x) {return x; } }
Expand All @@ -1967,6 +1996,22 @@ if (isCallable!(F))
assert(toDelegate(i2)(0xBED) == 0xBED);
}

@safe unittest
{
static void fun() @system pure nothrow @nogc
{
return;
}

auto fn = &fun;
static assert( is(typeof(fn) == void function() @system pure nothrow @nogc));
static assert(!is(typeof(fn) == void function() @safe pure nothrow @nogc));

auto dg = fn.toDelegate();
static assert( is(typeof(dg) == void delegate() @system pure nothrow @nogc));
static assert(!is(typeof(dg) == void delegate() @safe pure nothrow @nogc));
}

/**
* Passes the fields of a struct as arguments to a function.
*
Expand Down
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