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[SystemZ][z/OS] vasprintf fix libc++

Authored by muiez on Feb 25 2021, 6:49 AM.


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rGf6af5efcec41: [SystemZ][z/OS] vasprintf fix libc++

The aim is to use the correct vasprintf implementation for z/OS libc++, where a copy of va_list ap is needed. In particular, it avoids the potential that the initial internal call to vsnprintf will modify ap and the subsequent call to vsnprintf will use that modified ap.

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muiez requested review of this revision.Feb 25 2021, 6:49 AM
muiez created this revision.
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ldionne requested changes to this revision.Mar 1 2021, 10:41 AM

We have the same issue in __libcpp_vasprintf in libcxx/src/support/win32/locale_win32.cpp - we should fix both in one go.


Is there a reason for calling vsnprintf twice unconditionally now instead of doing the same thing as before, but providing a copy of the va_list for the first call?

In other words, why not do:

static inline
int vasprintf(char **strp, const char *fmt, va_list ap)
  const size_t buff_size = 256;
  if ((*strp = (char *)malloc(buff_size)) == NULL)
    return -1;

  va_list ap_copy;
  va_copy(ap_copy, ap);
  int str_size = vsnprintf(*strp, buff_size, fmt,  ap_copy);

  if (str_size >= buff_size)
    if ((*strp = (char *)realloc(*strp, str_size + 1)) == NULL)
      return -1;
    str_size = vsnprintf(*strp, str_size + 1, fmt,  ap);
  return str_size;
This revision now requires changes to proceed.Mar 1 2021, 10:41 AM
muiez updated this revision to Diff 328517.Mar 5 2021, 7:11 AM

modify old implementation, formatting

muiez updated this revision to Diff 328520.Mar 5 2021, 7:19 AM

win32 __libcpp_vasprintf fix

muiez added a comment.Mar 8 2021, 6:30 AM

Any ideas as to why the CI build failed with mainly FileNotFoundError for Apple system? The changes seem unrelated.

Quuxplusone requested changes to this revision.Mar 8 2021, 6:43 AM
Quuxplusone added a subscriber: Quuxplusone.
Quuxplusone added inline comments.
122 ↗(On Diff #328520)

I don't think you need this diff. We receive a va_list; we pass it (once) to __libcpp_vasprintf. One source, one sink. No copy should be needed.

However, you do need to modify __libcpp_vasprintf in src/support/win32/support.cpp per Louis' comment.

This revision now requires changes to proceed.Mar 8 2021, 6:43 AM
muiez updated this revision to Diff 329065.Mar 8 2021, 10:32 AM

fix for win32

Quuxplusone accepted this revision as: Quuxplusone.Mar 8 2021, 10:56 AM

Okay, my comments have been resolved.

@ldionne May we get a review please? Thanks

@ldionne is on vacation this month, so don't expect anything from him until April, presumably.
@curdeius perhaps?
However, (1) since Louis did have specific "requested changes," it might be appropriate to wait for him before landing this, anyway.
(2) this varargs stuff is similar to D98097 — just in a different part of the codebase — and you might want to compare the two snippets and see if they could be even further harmonized. (Perhaps by leaving review comments on D98097.)

ldionne accepted this revision.Mar 18 2021, 10:38 AM
This revision is now accepted and ready to land.Mar 18 2021, 10:38 AM
This revision was automatically updated to reflect the committed changes.