threads / bug / 56806

[Bug] wrapper.c uses unportable unsetenv

Subject: [Bug] wrapper.c uses unportable unsetenv

## tl;dr

7 messages between Oct 29, 2021 and Oct 29, 2021.

replies: 6people: 3as markdown or json

rsbecker@nexbridge.com· Oct 29, 2021, 20:14 UTC · lore

The unsetenv()/setenv(overwrite) calls are not 100% portable - as in not on all POSIX implementations. It breaks the build on some of the NonStop platforms. This will change in a year or two but I really don't want to fall behind on git releases.

This was introduced at 3540c71 but I was on vacation when it happened so did not catch it during reviews - my apologies for that.

Is it critical that this be called or can we #ifdef it away if it isn't supported for a build? The #if is exactly this:

wrapper.c@150
+ #if (_TANDEM_ARCH_ > 3 || (_TANDEM_ARCH_ == 3 && __L_Series_RVU >= 2010))
	if (setenv(name, value, overwrite))
		die_errno(_("could not setenv '%s'"), name ? name :
"(null)");
+ #endif
wrapper.c@154
+ #if (_TANDEM_ARCH_ > 3 || (_TANDEM_ARCH_ == 3 && __L_Series_RVU >= 2010))
	if (!unsetenv(name))
		die_errno(_("could not unsetenv '%s'"), name ? name :
"(null)");
+ #endif
-Randall
Junio C Hamano· Oct 29, 2021, 20:35 UTC · re: rsbecker@nexbridge.com · lore

Re: [Bug] wrapper.c uses unportable unsetenv

<rsbecker@nexbridge.com> writes:
Show 7 quoted lines
> The unsetenv()/setenv(overwrite) calls are not 100% portable - as in not on
> all POSIX implementations. It breaks the build on some of the NonStop
> platforms. This will change in a year or two but I really don't want to fall
> behind on git releases.
>
> This was introduced at 3540c71 but I was on vacation when it happened so did
> not catch it during reviews - my apologies for that.

I do not quite understand. xsetenv() does use the three-arg setenv(), but that is not anything new. It merely replaced a call to the same three-arg setenv() in environment.c that have already been there, introduced by d7ac12b2 (Add set_git_dir() function, 2007-08-01).

You may argue that 3540c71 has done a shoddy job by introducing xunsetenv() without adding any caller, and to this day, we do not have a single caller to the wrapper, but we already have a few calls to unsetenv() that is compiled unconditionally.

So if you built any version of Git, you must have had these somehow "available" in your build (e.g. your system headers may have made them a no-op), and I'd expect you'd keep doing the same to locally work it around on the platform side, without ...

> Is it critical that this be called or can we #ifdef it away if it isn't
> supported for a build? The #if is exactly this:

... doing something like this in the generic part of the code. Please don't do this.

Show 13 quoted lines
> wrapper.c@150
> + #if (_TANDEM_ARCH_ > 3 || (_TANDEM_ARCH_ == 3 && __L_Series_RVU >= 2010))
> 	if (setenv(name, value, overwrite))
> 		die_errno(_("could not setenv '%s'"), name ? name :
> "(null)");
> + #endif
>
> wrapper.c@154
> + #if (_TANDEM_ARCH_ > 3 || (_TANDEM_ARCH_ == 3 && __L_Series_RVU >= 2010))
> 	if (!unsetenv(name))
> 		die_errno(_("could not unsetenv '%s'"), name ? name :
> "(null)");
> + #endif

There are compat/setenv.c and compat/unsetenv.c to be used when NO_SETENV and NO_UNSETENV are defined. Is that how you built your Git earlier since 2007, perhaps?

rsbecker@nexbridge.com· Oct 29, 2021, 20:49 UTC · re: Junio C Hamano · lore

RE: [Bug] wrapper.c uses unportable unsetenv

On October 29, 2021 4:35 PM, Junio C Hamano:
Show 11 quoted lines
> <rsbecker@nexbridge.com> writes:
> 
> > The unsetenv()/setenv(overwrite) calls are not 100% portable - as in
> > not on all POSIX implementations. It breaks the build on some of the
> > NonStop platforms. This will change in a year or two but I really
> > don't want to fall behind on git releases.
> >
> > This was introduced at 3540c71 but I was on vacation when it happened
> > so did not catch it during reviews - my apologies for that.
> 
> I do not quite understand.  xsetenv() does use the three-arg setenv(), but
that is
> not anything new.  It merely replaced a call to the same three-arg
setenv() in
Show 5 quoted lines
> environment.c that have already been there, introduced by d7ac12b2 (Add
> set_git_dir() function, 2007-08-01).
> 
> You may argue that 3540c71 has done a shoddy job by introducing
> xunsetenv() without adding any caller, and to this day, we do not have a
single
> caller to the wrapper, but we already have a few calls to unsetenv() that
is
> compiled unconditionally.
> 
> So if you built any version of Git, you must have had these somehow
"available"
> in your build (e.g. your system headers may have made them a no-op), and
I'd
> expect you'd keep doing the same to locally work it around on the platform
side,
Show 28 quoted lines
> without ...
> 
> > Is it critical that this be called or can we #ifdef it away if it
> > isn't supported for a build? The #if is exactly this:
> 
> ... doing something like this in the generic part of the code.
> Please don't do this.
> 
> > wrapper.c@150
> > + #if (_TANDEM_ARCH_ > 3 || (_TANDEM_ARCH_ == 3 && __L_Series_RVU >=
> > + 2010))
> > 	if (setenv(name, value, overwrite))
> > 		die_errno(_("could not setenv '%s'"), name ? name :
> > "(null)");
> > + #endif
> >
> > wrapper.c@154
> > + #if (_TANDEM_ARCH_ > 3 || (_TANDEM_ARCH_ == 3 && __L_Series_RVU >=
> > + 2010))
> > 	if (!unsetenv(name))
> > 		die_errno(_("could not unsetenv '%s'"), name ? name :
> > "(null)");
> > + #endif
> 
> 
> There are compat/setenv.c and compat/unsetenv.c to be used when
> NO_SETENV and NO_UNSETENV are defined.  Is that how you built your Git
> earlier since 2007, perhaps?

We have defined NO_SETENV and NO_UNSETENV since I have been maintaining it, so I don't get how we are getting into this situation. I was planning on removing NO_SETENV when the OS caught up for that on our minimum support builds next year. NO_UNSETENV needs to stick around for bit longer. The setenv() code is actually fine. It is unsetenv() that is causing problems. Should not git-compat-util.h be included in wrapper.c so that we reference gitunsetenv?

rsbecker@nexbridge.com· Oct 29, 2021, 21:10 UTC · re: rsbecker@nexbridge.com · lore

RE: [Bug] wrapper.c uses unportable unsetenv

On October 29, 2021 4:50 PM, I wrote:
Show 7 quoted lines
> To: 'Junio C Hamano' <gitster@pobox.com>
> Cc: git@vger.kernel.org
> Subject: RE: [Bug] wrapper.c uses unportable unsetenv
> 
> On October 29, 2021 4:35 PM, Junio C Hamano:
> > <rsbecker@nexbridge.com> writes:
> >
<snip>
Show 6 quoted lines
> > There are compat/setenv.c and compat/unsetenv.c to be used when
> > NO_SETENV and NO_UNSETENV are defined.  Is that how you built your Git
> > earlier since 2007, perhaps?
> 
> We have defined NO_SETENV and NO_UNSETENV since I have been maintaining
> it, so I don't get how we are getting into this situation. I was planning
on
Show 5 quoted lines
> removing NO_SETENV when the OS caught up for that on our minimum support
> builds next year. NO_UNSETENV needs to stick around for bit longer. The
> setenv() code is actually fine. It is unsetenv() that is causing problems.
> Should not git-compat-util.h be included in wrapper.c so that we reference
> gitunsetenv?
The actual issue is this:
        if (!unsetenv(name))
            ^
"/home/ituglib/randall/git/wrapper.c", line 156: error(134):  expression
must have arithmetic or pointer type

This is with NO_UNSETENV = YesPlease. It makes no sense to me why this isn't compiling.

Junio C Hamano· Oct 29, 2021, 21:42 UTC · re: rsbecker@nexbridge.com · lore

Re: [Bug] wrapper.c uses unportable unsetenv

<rsbecker@nexbridge.com> writes:
Show 9 quoted lines
> The actual issue is this:
>
>         if (!unsetenv(name))
>             ^
> "/home/ituglib/randall/git/wrapper.c", line 156: error(134):  expression
> must have arithmetic or pointer type
>
> This is with NO_UNSETENV = YesPlease. It makes no sense to me why this isn't
> compiling.

Ah, compat/unsetenv.c is broken. gitunsetenv() should return int, not void.

----- >8 --------- >8 --------- >8 --------- >8 --------- >8 -----
Subject: unsetenv(3) returns int, not void

This compatilibity implementation has been returning a wrong type, ever since 731043fd (Add compat/unsetenv.c ., 2006-01-25) added to the system, yet nobody noticed it in the past 16 years, presumably because no code checks failures in their unsetenv() calls. Sigh.

For now, make it always succeed.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 compat/unsetenv.c | 2 +-
 git-compat-util.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git c/compat/unsetenv.c w/compat/unsetenv.c
index bf5fd7063b..46d49c2c5e 100644
--- c/compat/unsetenv.c
+++ w/compat/unsetenv.c
@@ -1,6 +1,6 @@
 #include "../git-compat-util.h"
 
-void gitunsetenv (const char *name)
+int gitunsetenv(const char *name)
 {
 #if !defined(__MINGW32__)
      extern char **environ;
diff --git c/git-compat-util.h w/git-compat-util.h
index b46605300a..0f7e369a5d 100644
--- c/git-compat-util.h
+++ w/git-compat-util.h
@@ -726,7 +726,7 @@ char *gitmkdtemp(char *);
 
 #ifdef NO_UNSETENV
 #define unsetenv gitunsetenv
-void gitunsetenv(const char *);
+int gitunsetenv(const char *);
 #endif
 
 #ifdef NO_STRCASESTR
Johannes Schindelin· Oct 29, 2021, 21:50 UTC · re: Junio C Hamano · lore

Re: [Bug] wrapper.c uses unportable unsetenv

Hi Junio,
On Fri, 29 Oct 2021, Junio C Hamano wrote:
Show 9 quoted lines
> ----- >8 --------- >8 --------- >8 --------- >8 --------- >8 -----
> Subject: unsetenv(3) returns int, not void
> 
> This compatilibity implementation has been returning a wrong type,
> ever since 731043fd (Add compat/unsetenv.c ., 2006-01-25) added to
> the system, yet nobody noticed it in the past 16 years, presumably
> because no code checks failures in their unsetenv() calls.  Sigh.
> 
> For now, make it always succeed.
Makes sense, but...
Show 18 quoted lines
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  compat/unsetenv.c | 2 +-
>  git-compat-util.h | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git c/compat/unsetenv.c w/compat/unsetenv.c
> index bf5fd7063b..46d49c2c5e 100644
> --- c/compat/unsetenv.c
> +++ w/compat/unsetenv.c
> @@ -1,6 +1,6 @@
>  #include "../git-compat-util.h"
>  
> -void gitunsetenv (const char *name)
> +int gitunsetenv(const char *name)
>  {
>  #if !defined(__MINGW32__)
>       extern char **environ;
... but we are missing this:
@@ -24,4 +24,5 @@ void gitunsetenv (const char *name)
 	  ++dst;
      }
      environ[dst] = NULL;
+     return 0;
 }

Thanks,
Dscho

> diff --git c/git-compat-util.h w/git-compat-util.h
> index b46605300a..0f7e369a5d 100644
> --- c/git-compat-util.h
> +++ w/git-compat-util.h
> @@ -726,7 +726,7 @@ char *gitmkdtemp(char *);
>  
>  #ifdef NO_UNSETENV
>  #define unsetenv gitunsetenv
> -void gitunsetenv(const char *);
> +int gitunsetenv(const char *);
>  #endif
>  
>  #ifdef NO_STRCASESTR
> 
> 
> 
>
Junio C Hamano· Oct 29, 2021, 21:57 UTC · re: Johannes Schindelin · lore

Re: [Bug] wrapper.c uses unportable unsetenv

Johannes Schindelin <johannes.schindelin@gmail.com> writes:
Show 6 quoted lines
> @@ -24,4 +24,5 @@ void gitunsetenv (const char *name)
>  	  ++dst;
>       }
>       environ[dst] = NULL;
> +     return 0;
>  }

Yup, that hunk (with a blank before the "return") is already in my "real" version. Thanks for spotting.

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