https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99232
Bug ID: 99232
Summary: Exported variable in module gives error: 'lambda' was
not declared in this scope
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: patrick.kox at commandoregel dot be
Target Milestone: ---
When compiling Ex11-01 from the book "Beginning C++20" by Horton and Van Weert
there is an error message that the exported variable (const double) was not
declared.
here is the code:
//math.cpp
export module math;
export auto square(const auto& x) { return x * x; } // An abbreviated function
template
export const double lambda{1.303577269034296391257}; // Conway's
constant
export enum class Oddity { Even, Odd };
bool isOdd(int x) { return x % 2 != 0; } // Module-local function (not
exported)
export auto getOddity(int x) { return isOdd(x) ? Oddity::Odd : Oddity::Even; }
//-------------------------------
// main.cpp
// Consuming your own module
import <iostream>;
#define FMT_HEADER_ONLY
#include "fmt/format.h"
import math;
int main()
{
std::cout << "Lambda squared: " << square(lambda) << std::endl;
int number;
std::cout << "\nPlease enter an odd number: ";
std::cin >> number;
std::cout << std::endl;
switch (getOddity(number))
{
using enum Oddity;
case Odd:
std::cout << "Well done! And remember: you have to be odd to be number
one!";
break;
case Even:
fmt::print("Odd, {} seems to be even?", number);
break;
}
std::cout << std::endl;
}
//-------------------------------
To compile I do the following:
1. copy iostream into my source directory
2. execute the command: g++ -Wall -Wextra -fmodules-ts -std=c++20 -c -x
c++-system-header iostream
3. execute the command: g++ -fmodules-ts -Wall -Wextra -std=c++20 -pedantic
-pthread -lfmt math.cpp main.cpp
//-------------------------------
The full error message is:
main.cpp: In function ‘int main()’:
main.cpp:13:45: error: ‘lambda’ was not declared in this scope
13 | std::cout << "Lambda squared: " << square(lambda) << std::endl;
|
//-------------------------------
If I move the declaration of the lambda variable to the main.cpp sourcefile the
code does compile, so the other exports seem to work correctly.
the version of GCC is: g++ (GCC) 11.0.0 20210214 (experimental)
