Go patch committed: Change name mangling convention

Go patch committed: Change name mangling convention

[Ian Lance Taylor]

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This patch to the Go frontend and libgo changes the name mangling
convention.  The previous convention (which was actually the second
one) turned out to be ambiguous when the path to a package contained a
dot; this is a common case, as many package paths are of the form
"github.com/name/package".  The previous convention also did not
support package paths that start with a digit, which is less common
but does occur (https://golang.org/issue/41862).

This patch rewrites and somewhat simplifies the naming convention.
Now dot is used only as a separator character and for special names.
Actual name mangling, for representing Unicode characters and other
non-ASCII alphanumerics, is now done with an underscore.  This has the
advantage of being simpler, in that it avoids the overloading that the
previous convention applied to dot.  It has the disadvantage that
mangled symbol names look somewhat like valid Go names, since valid Go
names can of course contain underscore.  Still, it seems like the best
choice.

This patch increments the libgo major version number, since many
symbol names have changed.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

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Re: Go patch committed: Change name mangling convention

[Rainer Orth]

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Hi Ian,

> This patch to the Go frontend and libgo changes the name mangling
> convention.  The previous convention (which was actually the second
> one) turned out to be ambiguous when the path to a package contained a
> dot; this is a common case, as many package paths are of the form
> "github.com/name/package".  The previous convention also did not
> support package paths that start with a digit, which is less common
> but does occur (https://golang.org/issue/41862).
>
> This patch rewrites and somewhat simplifies the naming convention.
> Now dot is used only as a separator character and for special names.
> Actual name mangling, for representing Unicode characters and other
> non-ASCII alphanumerics, is now done with an underscore.  This has the
> advantage of being simpler, in that it avoids the overloading that the
> previous convention applied to dot.  It has the disadvantage that
> mangled symbol names look somewhat like valid Go names, since valid Go
> names can of course contain underscore.  Still, it seems like the best
> choice.
>
> This patch increments the libgo major version number, since many
> symbol names have changed.
>
> Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
> to mainline.

this patch broke Solaris bootstrap: linking in gotools fails with

Undefined                       first referenced
 symbol                             in file
log_1syslog.syslog__c               ../i386-pc-solaris2.11/libgo/.libs/libgo.so
ld: fatal: symbol referencing errors
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:829: buildid] Error 1

The following patch fixed this for me:


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diff --git a/libgo/go/log/syslog/syslog_c.c b/libgo/go/log/syslog/syslog_c.c
--- a/libgo/go/log/syslog/syslog_c.c
+++ b/libgo/go/log/syslog/syslog_c.c
@@ -12,7 +12,7 @@
    can't represent a C varargs function in Go.  */
 
 void syslog_c(intgo, const char*)
-  __asm__ (GOSYM_PREFIX "log_1syslog.syslog_c");
+  __asm__ (GOSYM_PREFIX "log_1syslog.syslog__c");
 
 void
 syslog_c (intgo priority, const char *msg)

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	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University

Re: Go patch committed: Change name mangling convention

[Ian Lance Taylor]

On Sun, Nov 22, 2020 at 11:00 AM Rainer Orth
<ro@cebitec.uni-bielefeld.de> wrote:
>
> > This patch to the Go frontend and libgo changes the name mangling
> > convention.  The previous convention (which was actually the second
> > one) turned out to be ambiguous when the path to a package contained a
> > dot; this is a common case, as many package paths are of the form
> > "github.com/name/package".  The previous convention also did not
> > support package paths that start with a digit, which is less common
> > but does occur (https://golang.org/issue/41862).
> >
> > This patch rewrites and somewhat simplifies the naming convention.
> > Now dot is used only as a separator character and for special names.
> > Actual name mangling, for representing Unicode characters and other
> > non-ASCII alphanumerics, is now done with an underscore.  This has the
> > advantage of being simpler, in that it avoids the overloading that the
> > previous convention applied to dot.  It has the disadvantage that
> > mangled symbol names look somewhat like valid Go names, since valid Go
> > names can of course contain underscore.  Still, it seems like the best
> > choice.
> >
> > This patch increments the libgo major version number, since many
> > symbol names have changed.
> >
> > Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
> > to mainline.
>
> this patch broke Solaris bootstrap: linking in gotools fails with
>
> Undefined                       first referenced
>  symbol                             in file
> log_1syslog.syslog__c               ../i386-pc-solaris2.11/libgo/.libs/libgo.so
> ld: fatal: symbol referencing errors
> collect2: error: ld returned 1 exit status
> make[2]: *** [Makefile:829: buildid] Error 1
>
> The following patch fixed this for me:

Thanks.  Committed to mainline.

Ian