arphaman created this revision.
arphaman added reviewers: vsapsai, rsmith, george.burgess.iv.
The commit r316245 introduced a regression that causes an assertion failure
when Clang tries to cast an `IncompleteArrayType` to a `PointerType` when
evaluating __builtin_object_size in this sample:
typedef struct {
char string[512];
} NestedArrayStruct;
typedef struct {
int x;
NestedArrayStruct session[];
} IncompleteArrayStruct;
void func(IncompleteArrayStruct* p) {
__builtin___strlcpy_chk (p->session[0].string, "ab", 2,
__builtin_object_size(p->session[0].string, 1));
}
Interestingly enough gcc seems to produce a different output for the above code
(when `1` is the last parameter to `__builtin_object_size`). It evaluates
`__builtin_object_size` to 512 instead of -1 like Clang:
https://godbolt.org/g/vD9F9T
I'm still not sure what's the right behavior after reading GCC's description of
__builtin_object_size
(https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html). Maybe someone
who's more familiar with this builtin could point to the cause of this
discrepancy.
rdar://36094951
Repository:
rC Clang
https://reviews.llvm.org/D41405
Files:
lib/AST/ExprConstant.cpp
test/Sema/builtin-object-size.c
Index: test/Sema/builtin-object-size.c
===================================================================
--- test/Sema/builtin-object-size.c
+++ test/Sema/builtin-object-size.c
@@ -91,3 +91,16 @@
return n;
}
+
+typedef struct {
+ char string[512];
+} NestedArrayStruct;
+
+typedef struct {
+ int x;
+ NestedArrayStruct session[];
+} IncompleteArrayStruct;
+
+void rd36094951_IAS_builtin_object_size_assertion(IncompleteArrayStruct* p) {
+ __builtin___strlcpy_chk (p->session[0].string, "ab", 2,
__builtin_object_size(p->session[0].string, 1));
+}
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -7419,7 +7419,10 @@
// If we don't know the array bound, conservatively assume we're looking at
// the final array element.
++I;
- BaseType = BaseType->castAs<PointerType>()->getPointeeType();
+ if (BaseType->isIncompleteArrayType())
+ BaseType = Ctx.getAsArrayType(BaseType)->getElementType();
+ else
+ BaseType = BaseType->castAs<PointerType>()->getPointeeType();
}
for (unsigned E = LVal.Designator.Entries.size(); I != E; ++I) {
Index: test/Sema/builtin-object-size.c
===================================================================
--- test/Sema/builtin-object-size.c
+++ test/Sema/builtin-object-size.c
@@ -91,3 +91,16 @@
return n;
}
+
+typedef struct {
+ char string[512];
+} NestedArrayStruct;
+
+typedef struct {
+ int x;
+ NestedArrayStruct session[];
+} IncompleteArrayStruct;
+
+void rd36094951_IAS_builtin_object_size_assertion(IncompleteArrayStruct* p) {
+ __builtin___strlcpy_chk (p->session[0].string, "ab", 2, __builtin_object_size(p->session[0].string, 1));
+}
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -7419,7 +7419,10 @@
// If we don't know the array bound, conservatively assume we're looking at
// the final array element.
++I;
- BaseType = BaseType->castAs<PointerType>()->getPointeeType();
+ if (BaseType->isIncompleteArrayType())
+ BaseType = Ctx.getAsArrayType(BaseType)->getElementType();
+ else
+ BaseType = BaseType->castAs<PointerType>()->getPointeeType();
}
for (unsigned E = LVal.Designator.Entries.size(); I != E; ++I) {
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