Attempting to build the Windows version of DMD, the reference compiler for the D programming language, fails under Wine. This seems to be caused by the following chain of events:

1. The makefile invokes a build program with a "VERBOSE=" on the command-line:

   https://github.com/dlang/dmd/blob/49dfbe54f4a0f62a0694aec9fb4184739903a0c2/src/win32.mak#L81

   (Here "$(VERBOSE)" is not set and expands to the empty string.)

2. The build program registers the command-line arguments into the process environment:

   https://github.com/dlang/dmd/blob/49dfbe54f4a0f62a0694aec9fb4184739903a0c2/src/build.d#L1359

   This sets the environment variable VERBOSE to the empty string.

3. Later, it attempts to check if the "VERBOSE" variable is in the environment:

   https://github.com/dlang/dmd/blob/49dfbe54f4a0f62a0694aec9fb4184739903a0c2/src/build.d#L1379

4. This calls the following Windows code in the standard library to read the environment:

   https://github.com/dlang/phobos/blob/e373b4e77448bc11c6e4ea6c85bcdb8f7ab86f20/std/process.d#L3506-L3515

5. For empty variables, the code behaves differently in Windows and Wine - Wine's implementation returns 0, while Windows returns 1. As a result, the standard library code throws an exception under Wine.

Writing a test program reveals further differences. The program:


#include <stdio.h>
#include <windows.h>

void main()
{
	WCHAR buf[4];
	DWORD size;
	int len, i;

	for (len = 0; len <= 2; len++)
	{
		for (i = 0; i < len; i++)
			buf[i] = 'a';
		buf[len] = 0;	

		SetEnvironmentVariableW(L"TESTVAR", buf);

		for (i = 0; i <= len + 1; i++)
		{
			DWORD err;
			SetLastError(1);
			buf[0] = 1;
			size = GetEnvironmentVariableW(L"TESTVAR", buf, i);
			err = GetLastError();
			printf("%d->%d: size=%d error=%d buf[0]=%d\n", 
				len, i, size, err, buf[0]);
		}
		printf("\n");
	}	
}


Output on Windows [Version 10.0.17134.648]:

0->0: size=1 error=1 buf[0]=1
0->1: size=0 error=1 buf[0]=0

1->0: size=2 error=1 buf[0]=1
1->1: size=2 error=1 buf[0]=0
1->2: size=1 error=1 buf[0]=97

2->0: size=3 error=1 buf[0]=1
2->1: size=3 error=1 buf[0]=0
2->2: size=3 error=1 buf[0]=0
2->3: size=2 error=1 buf[0]=97

Output on Wine:

0->0: size=0 error=1 buf[0]=1
0->1: size=0 error=1 buf[0]=0

1->0: size=2 error=122 buf[0]=1
1->1: size=2 error=122 buf[0]=1
1->2: size=1 error=1 buf[0]=97

2->0: size=3 error=122 buf[0]=1
2->1: size=3 error=122 buf[0]=1
2->2: size=3 error=122 buf[0]=1
2->3: size=2 error=1 buf[0]=97

We can observe these differences:

1. Wine returns 0 and not 1 when the variable is empty and the function is given a zero-length buffer.

2. Wine sets the last error to ERROR_INSUFFICIENT_BUFFER, while Windows doesn't.

3. Windows zeroes the buffer if the size is non-zero but still insufficient to hold the value. (This is not a bug as the behavior is specified in the documentation to be undefined.)