[binutils-gdb] Fix "set cwd ..." on Cygwin, part 1

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e922d7b7c19e7f2d0b77f1eb182049c907e669dd

commit e922d7b7c19e7f2d0b77f1eb182049c907e669dd
Author: Pedro Alves <[email protected]>
Date:   Wed May 20 13:14:07 2026 +0100

    Fix "set cwd ..." on Cygwin, part 1
    
    When running gdb.base/exitsignal.exp on Cygwin, we see:
    
     (gdb) set cwd /cygdrive/d/cygwin-gdb/build-testsuite/outputs/gdb.base/exitsignal
     (gdb) run
     Starting program: /cygdrive/d/cygwin-gdb/build-testsuite/outputs/gdb.base/exitsignal/exitsignal
     Error converting inferior cwd: 28
     (gdb) FAIL: gdb.base/exitsignal.exp: runto: run to main
    
    28 is ENOSPC.  But this isn't really literally no space left, though.
    cygwin_conv_path documentation mentions that error code.
    
    According to the Cygwin API documentation for cygwin_conv_path, the
    function fails with ENOSPC ("No space left on device") when the size
    of the destination buffer is smaller than what is required for the
    conversion.  See:
    
     https://cygwin.com/cygwin-api/func-cygwin-conv-path.html
    
    If we look closely at how the buffer size argument is being passed, we
    see we have two problems here:
    
    1) Incorrectly passing down the input buffer size instead of the
    output size.
    
    The code passes strlen(inferior_cwd) as the size of the destination
    buffer (infcwd). However, the target Windows path format
    (e.g. "D:\cygwin-gdb\..." in my case) could be longer or shorter than
    the POSIX source path ("/cygdrive/d/...").  In my specific case, the
    source string is 64 characters, while the target Windows string is 61
    (wide) characters (and twice as many bytes).
    
    2) Incorrectly passing character count instead of byte count
    
    The conversion target token is CCP_POSIX_TO_WIN_W.  The _W means that
    the destination buffer infcwd takes wide characters (wchar_t).  The
    documentation states that the size argument is in bytes, not
    characters.
    
    This commit fixes it, by passing the byte size of the destination
    buffer.
    
    Approved-By: Tom Tromey <[email protected]>
    Change-Id: I70af6ef394f48da35ccc2e04ef764915e09e59de
    commit-id: 66c930c2

Diff:
---
 gdb/windows-nat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index d506b42fbda..862568fa21e 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -2925,7 +2925,7 @@ windows_nat_target::create_inferior (const char *exec_file,
 
   if (inferior_cwd != NULL
       && cygwin_conv_path (CCP_POSIX_TO_WIN_W, inferior_cwd,
-			   infcwd, strlen (inferior_cwd)) < 0)
+			   infcwd, sizeof (infcwd)) < 0)
     error (_("Error converting inferior cwd: %d"), errno);
 
   args = (wchar_t *) alloca ((wcslen (toexec) + wcslen (cygallargs) + 2)