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g++: deducing this in recursive lambdas fails to compile #22878

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2 of 6 tasks
cuellius opened this issue Dec 22, 2024 · 4 comments
Closed
2 of 6 tasks

g++: deducing this in recursive lambdas fails to compile #22878

cuellius opened this issue Dec 22, 2024 · 4 comments
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external Issues caused by external software or project which is not related to msys2 GCC

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@cuellius
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Description / Steps to reproduce the issue

Consider the following code:

main.cpp -- deducing this version 
#include <iostream>
#include <vector>
#include <sstream>
#include <algorithm>
#include <numeric>
#include <functional>

int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int t;
    std::cin >> t;

    for (int tt = 0; tt < t; tt++)
    {
        int n;
        long long x, y;

        std::cin >> n >> x >> y;

        std::vector<long long> a(n);
        for (int i = 0; i < n; i++) std::cin >> a[i];

        std::vector<long long> tree[(n + 7) << 2];

        auto tree_build = [&](this auto const &tree_build, int v, int tl, int tr) -> void
        {
            if (tl == tr)
                tree[v] = { a[tl] };
            else
            {
                int tm = (tl + tr) >> 1;
                tree_build(v << 1, tl, tm);
                tree_build((v << 1) | 1, tm + 1, tr);
                std::merge(tree[v << 1].begin(), tree[v << 1].end(),
                           tree[(v << 1) | 1].begin(), tree[(v << 1) | 1].end(),
                           std::back_inserter(tree[v]));
            }
        };

        //std::function<long long(int, int, int, int, int, long long, long long)> tree_query;
        auto tree_query = [&](this auto const &tree_query, int v, int tl, int tr, int l, int r, long long low, long long high) -> long long
        {
            if (l > r)
                return 0;
            if (l == tl && tr == r)
            {
                auto it_low = std::lower_bound(tree[v].begin(), tree[v].end(), low);
                auto it_high = std::upper_bound(tree[v].begin(), tree[v].end(), high);
                return std::distance(it_low, it_high);
            }

            int tm = (tl + tr) >> 1;
            return tree_query(v << 1, tl, tm, l, std::min(r, tm), low, high) +
                   tree_query((v << 1) | 1, tm + 1, tr, std::max(l,tm+1), r, low, high);
        };

        //tree_build(1, 0, n - 1);

        long long sum = std::accumulate(a.begin(), a.end(), 0ll), ans = 0;
        for (int i = 0; i < n - 1; i++)
        {
            //x <= sum - a[i] - a[j] <= y
            //x - sum + a[i] <= -a[j] <= y - sum + a[i]
            //sum - a[i] - y <= a[j] <= sum - a[i] - x
            ans += tree_query(1, 0, n - 1, i + 1, n - 1, sum - a[i] - y, sum - a[i] - x);
        }

        std::cout << ans << '\n';
    }

    return 0;
}

I compile it with g++ -O2 -std=c++23 main.cpp -o main, where main.cpp is a file with this code, and get the following message:

main.cpp: In lambda function:
main.cpp:31:17: internal compiler error: Segmentation fault
   31 |                 tree[v] = { a[tl] };
      |                 ^~~~
Please submit a full bug report, with preprocessed source (by using -freport-bug).
See <https://github.com/msys2/MINGW-packages/issues> for instructions.

Expected behavior

The code should be correctly compiled. It should behave something like the following code:

main.cpp -- std::function version 
#include <iostream>
#include <vector>
#include <sstream>
#include <algorithm>
#include <numeric>
#include <functional>

int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int t;
    std::cin >> t;

    for (int tt = 0; tt < t; tt++)
    {
        int n;
        long long x, y;

        std::cin >> n >> x >> y;

        std::vector<long long> a(n);
        for (int i = 0; i < n; i++) std::cin >> a[i];

        std::vector<long long> tree[(n + 7) << 2];
        std::function<void(int, int, int)> tree_build;
        tree_build = [&](int v, int tl, int tr) -> void
        {
            if (tl == tr)
                tree[v] = { a[tl] };
            else
            {
                int tm = (tl + tr) >> 1;
                tree_build(v << 1, tl, tm);
                tree_build((v << 1) | 1, tm + 1, tr);
                std::merge(tree[v << 1].begin(), tree[v << 1].end(),
                           tree[(v << 1) | 1].begin(), tree[(v << 1) | 1].end(),
                           std::back_inserter(tree[v]));
            }
        };

        std::function<long long(int, int, int, int, int, long long, long long)> tree_query;
        tree_query = [&](int v, int tl, int tr, int l, int r, long long low, long long high) -> long long
        {
            if (l > r)
                return 0;
            if (l == tl && tr == r)
            {
                auto it_low = std::lower_bound(tree[v].begin(), tree[v].end(), low);
                auto it_high = std::upper_bound(tree[v].begin(), tree[v].end(), high);
                return std::distance(it_low, it_high);
            }

            int tm = (tl + tr) >> 1;
            return tree_query(v << 1, tl, tm, l, std::min(r, tm), low, high) +
                   tree_query((v << 1) | 1, tm + 1, tr, std::max(l,tm+1), r, low, high);
        };

        tree_build(1, 0, n - 1);

        long long sum = std::accumulate(a.begin(), a.end(), 0ll), ans = 0;
        for (int i = 0; i < n - 1; i++)
        {
            //x <= sum - a[i] - a[j] <= y
            //x - sum + a[i] <= -a[j] <= y - sum + a[i]
            //sum - a[i] - y <= a[j] <= sum - a[i] - x
            ans += tree_query(1, 0, n - 1, i + 1, n - 1, sum - a[i] - y, sum - a[i] - x);
        }

        std::cout << ans << '\n';
    }

    return 0;
}

std::function version successfully compiles.

Actual behavior

The code fails to compile.

The command g++ -std=c++23 -O2 -freport-bug main.cpp -o main gives:

main.cpp: In lambda function:
main.cpp:31:17: internal compiler error: Segmentation fault
   31 |                 tree[v] = { a[tl] };
      |                 ^~~~
Please submit a full bug report, with preprocessed source.
See <https://github.com/msys2/MINGW-packages/issues> for instructions.
g++: fatal error: cannot execute 'C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/14.2.0/cc1plus.exe': open temporary output file
compilation terminated.

But, I can manually execute C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/14.2.0/cc1plus.exe, so I submit report without -freport-bug output. It also asks for preprocessed source, so I attach it (zipped):
main.zip

Verification

Windows Version

MSYS_NT-10.0-22631

MINGW environments affected

  • MINGW64
  • MINGW32
  • UCRT64
  • CLANG64
  • CLANGARM64

Are you willing to submit a PR?

No response
@cuellius cuellius added the bug label Dec 22, 2024
@cuellius
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I don't know, since I don't use Linux now.

@Biswa96
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Biswa96 commented Dec 22, 2024

Congrats! The compilation fails in Linux too.

$ g++ -O2 -std=c++23 main.cpp -o main
main.cpp: In lambda function:
main.cpp:30:9: internal compiler error: Segmentation fault
   30 |         tree[v] = {a[tl]};
      |         ^~~~
0x21a922a internal_error(char const*, ...)
        ???:0
0x92c9b4 cp_type_quals(tree_node const*)
        ???:0
0x942bfd build_simple_component_ref(tree_node*, tree_node*)
        ???:0
0x7efffb add_capture(tree_node*, tree_node*, tree_node*, bool, bool, unsigned int*)
        ???:0
0x7f060b add_default_capture(tree_node*, tree_node*, tree_node*)
        ???:0
0x9cd270 c_common_parse_file()
        ???:0
Please submit a full bug report, with preprocessed source (by using -freport-bug).
Please include the complete backtrace with any bug report.
See <https://gitlab.archlinux.org/archlinux/packaging/packages/gcc/-/issues> for instructions.

$ g++ --version
g++ (GCC) 14.2.1 20240910

@Biswa96 Biswa96 added the GCC label Dec 22, 2024
@Biswa96
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Biswa96 commented Dec 22, 2024 •
edited
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Wait, clang++ also fails. I wonder if the code is valid C++ or something is conflicting with standard.

@mati865
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mati865 commented Dec 22, 2024

Regardless of code validity, the compiler should never ICE.

@MehdiChinoune MehdiChinoune closed this as not planned Won't fix, can't repro, duplicate, stale Dec 25, 2024
@MehdiChinoune MehdiChinoune added external Issues caused by external software or project which is not related to msys2 and removed bug labels Dec 25, 2024
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@mati865 @Biswa96 @cuellius @MehdiChinoune