[PATCH 15/30] nptl: Remove pread from libpthread

[Florian Weimer]

* Joseph Myers:

> On Wed, 17 Mar 2021, Florian Weimer via Libc-alpha wrote:
>
>> Ah I see it now: mips64-linux-gnu-n64 has only this:
>> 
>>  1556: 0000000000109b70    300 FUNC    GLOBAL DEFAULT       12 __libc_pread@@GLIBC_PRIVATE
>>  2229: 0000000000109b70    300 FUNC    WEAK   DEFAULT       12 pread@@GLIBC_2.2
>
> (Because MIPS didn't have glibc 2.1, so uses the shlib-versions feature of 
> skipping all versions between GLIBC_2.0 and GLIBC_2.2 and mapping them to 
> GLIBC_2.2.)
>
>> Likewise ia64-linux-gnu:
>> 
>>  1640: 00000000001bb180    528 FUNC    GLOBAL DEFAULT       11 __libc_pread@@GLIBC_PRIVATE
>>  2624: 00000000001bb180    528 FUNC    WEAK   DEFAULT       11 pread@@GLIBC_2.2
>
> (Because ia64 symbol versions for many libraries start at GLIBC_2.2.)

Ahh, so alpha isn't really an outlier after all?

Adhemerval, would you please check if you can write a condition in
generic code using OTHERLIB_COMPAT (libpthread, …) with the appropriate
version ranges?

OTHERLIB_COMPAT would have to be defined like this:

diff --git a/include/shlib-compat.h b/include/shlib-compat.h
index 4b224c2672..6303639f28 100644
--- a/include/shlib-compat.h
+++ b/include/shlib-compat.h
@@ -45,6 +45,14 @@
 
 #ifdef SHARED
 
+/* Like LIB_COMPAT, but can check versions in other libraries.  It is
+   not always false outside for !IS_IN (LIB).  */
+#define OTHERLIB_COMPAT(lib, introduced, obsoleted)	\
+  _LIB_COMPAT (lib, introduced, obsoleted)
+#define _OTHERLIB_COMPAT(lib, introduced, obsoleted)			\
+  (!(ABI_##lib##_##obsoleted - 0)					\
+   || ((ABI_##lib##_##introduced - 0) < (ABI_##lib##_##obsoleted - 0)))
+
 /* Similar to LIB_COMPAT, but evaluate to 0 for static build.  The
    compatibility code should be conditionalized with e.g.
    `#if SHLIB_COMPAT (libm, GLIBC_2_0, GLIBC_2_2)' for code introduced
@@ -79,6 +87,7 @@
 #else
 
 /* Not compiling ELF shared libraries at all, so never any old versions.  */
+# define OTHERLIB_COMPAT(lib, introduced, obsoleted)	0
 # define SHLIB_COMPAT(lib, introduced, obsoleted)	0
 
 /* No versions to worry about, just make this the global definition.  */


Thanks,
Florian