在C++ 14中使用泛型lambda的奇怪编译器行为

Question

我最近遇到了一个有趣的GCC怪癖,当使用泛型lambda(C++ 14特性允许使用autolambda参数)时.似乎使用auto而不是type,会以某种方式影响"this"指针的捕获方式.我在以下示例中重现了问题:

#include <cstdio>

class A { private:
    void method(int i) {
        printf("Method Call %d",i);
    }

public:
    void publicMethod() {
        auto lambda = [&] (const int k) { //problematic line
            method(k);                    //problematic line
        };
        lambda(42);
    } };

int main() {
    A a;
    a.publicMethod();
    return 0; }

上面的代码有效.当我将"有问题的行"更改为:

        auto lambda = [&] (const auto k) { //problematic line
            method(k);                     //problematic line

它不再编译,但添加"this"指针:

        auto lambda = [&] (const auto k) { //problematic line
            this->method(k);               //problematic line

解决了这个问题.我的问题是:这种行为有合理的理由吗？或者是GCC的非理性怪癖(也许应该报道)？

这是使用autowithout的情况下编译器的输出this

test.cpp: In lambda function:
test.cpp:12:13: internal compiler error: Segmentation fault
             method(k);
             ^
0x848ecc crash_signal
    ../../src/gcc/toplev.c:383
0xea28e5 size_binop_loc(unsigned int, tree_code, tree_node*, tree_node*)
    ../../src/gcc/fold-const.c:1768
0xee86d7 gimplify_compound_lval
    ../../src/gcc/gimplify.c:2039
0xee86d7 gimplify_expr(tree_node**, gimple_statement_base**, gimple_statement_base**, bool (*)(tree_node*), int)
    ../../src/gcc/gimplify.c:8052
0xeeb639 gimplify_arg(tree_node**, gimple_statement_base**, unsigned int)
    ../../src/gcc/gimplify.c:2271
0xeeb639 gimplify_call_expr
    ../../src/gcc/gimplify.c:2477
0xee89f2 gimplify_expr(tree_node**, gimple_statement_base**, gimple_statement_base**, bool (*)(tree_node*), int)
    ../../src/gcc/gimplify.c:8071
0xee8da7 gimplify_stmt(tree_node**, gimple_statement_base**)
    ../../src/gcc/gimplify.c:5519
0xee8da7 gimplify_cleanup_point_expr
    ../../src/gcc/gimplify.c:5295
0xee8da7 gimplify_expr(tree_node**, gimple_statement_base**, gimple_statement_base**, bool (*)(tree_node*), int)
    ../../src/gcc/gimplify.c:8463
0xee7ace gimplify_stmt(tree_node**, gimple_statement_base**)
    ../../src/gcc/gimplify.c:5519
0xee94db gimplify_bind_expr
    ../../src/gcc/gimplify.c:1136
0xee94db gimplify_expr(tree_node**, gimple_statement_base**, gimple_statement_base**, bool (*)(tree_node*), int)
    ../../src/gcc/gimplify.c:8297
0xee757f gimplify_stmt(tree_node**, gimple_statement_base**)
    ../../src/gcc/gimplify.c:5519
0xee757f gimplify_body(tree_node*, bool)
    ../../src/gcc/gimplify.c:9234
0xee72fd gimplify_function_tree(tree_node*)
    ../../src/gcc/gimplify.c:9388
0xe195e0 cgraph_node::analyze()
    ../../src/gcc/cgraphunit.c:634
0xe195e0 analyze_functions
    ../../src/gcc/cgraphunit.c:1024
0x127d1ab symbol_table::finalize_compilation_unit()
    ../../src/gcc/cgraphunit.c:2453
0xd37db5 cp_write_global_declarations()
    ../../src/gcc/cp/decl2.c:4843
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-5/README.Bugs> for instructions.

用GCC 5.3.1编译

Answer 1

谢谢您的评论。事实上，这是 GCC 错误 - 我的同事刚刚将其报告给 GCC 支持人员：

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69977