[lldb] Fix ForwardListFrontEnd::CalculateNumChildren #139805
Conversation
Fixes the calculation of the number of children for `std::forward_list` to no longer be capped. The calculation was capped by the value of `target.max-children-count`. This resulted in at least the following problems: 1. The summary formatter would display the incorrect size when the size was greater than `max-child-count`. 2. The elision marker (`...`) would not be shown when the number of elements was greater than `max-child-count`.
|
@llvm/pr-subscribers-lldb Author: Dave Lee (kastiglione) ChangesFixes the calculation of the number of children for This resulted in at least the following problems:
Full diff: https://github.com/llvm/llvm-project/pull/139805.diff 2 Files Affected:
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxList.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxList.cpp
index 30db5f15c388f..e3c200da6a0f5 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxxList.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxList.cpp
@@ -251,7 +251,7 @@ llvm::Expected<uint32_t> ForwardListFrontEnd::CalculateNumChildren() {
ListEntry current(m_head);
m_count = 0;
- while (current && m_count < m_list_capping_size) {
+ while (current) {
++m_count;
current = current.next();
}
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/forward_list/TestDataFormatterGenericForwardList.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/forward_list/TestDataFormatterGenericForwardList.py
index 185a24cf6dce3..1639d7275b407 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/forward_list/TestDataFormatterGenericForwardList.py
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/forward_list/TestDataFormatterGenericForwardList.py
@@ -53,13 +53,14 @@ def do_test(self, stdlib_type):
substrs=["target.max-children-count (unsigned) = 256"],
)
+ self.runCmd("settings set target.max-children-count 256", check=False)
self.expect(
"frame variable thousand_elts",
matching=False,
- substrs=["[256]", "[333]", "[444]", "[555]", "[666]", "..."],
+ substrs=["[256]", "[333]", "[444]", "[555]", "[666]"],
)
- self.runCmd("settings set target.max-children-count 3", check=False)
+ self.runCmd("settings set target.max-children-count 3", check=False)
self.expect(
"frame variable thousand_elts",
matching=False,
@@ -73,7 +74,7 @@ def do_test(self, stdlib_type):
self.expect(
"frame variable thousand_elts",
matching=True,
- substrs=["size=256", "[0]", "[1]", "[2]", "..."],
+ substrs=["size=1000", "[0]", "[1]", "[2]", "..."],
)
def do_test_ptr_and_ref(self, stdlib_type):
@@ -138,7 +139,7 @@ def do_test_ptr_and_ref(self, stdlib_type):
"frame variable ref",
matching=True,
substrs=[
- "size=256",
+ "size=1000",
"[0] = 999",
"[1] = 998",
"[2] = 997",
@@ -149,7 +150,7 @@ def do_test_ptr_and_ref(self, stdlib_type):
"frame variable *ptr",
matching=True,
substrs=[
- "size=256",
+ "size=1000",
"[0] = 999",
"[1] = 998",
"[2] = 997",
|
|
I'm very much in favor of removing this dependence on the setting value, as I think it should be handled at a higher level. However, I fear this is going to make printing large std::forward_list very slow. Since computing the size of the list requires iterating through all the elements, which is a lot of pointer chasing, printing of large lists (like, 10k elements or more) could take a very long time (and I think that's the reason this limit was originally introduced). Fortunately, we already have a mechanism to prevent this -- we mave For this, I think the fix is to change the formatter to not print the exact size (all the time). For example, it could call The value of |
Fixes the calculation of the number of children for
std::forward_listto no longer becapped. The calculation was capped by the value of
target.max-children-count.This resulted in at least the following problems:
max-child-count....) would not be shown when the number of elements was greaterthan
max-child-count.