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authorJoseph Myers <joseph@codesourcery.com>2018-12-10 22:56:59 +0000
committerJoseph Myers <joseph@codesourcery.com>2018-12-10 22:56:59 +0000
commitcb7be1590e9b18e272e72eb4e910a7ad06a53bd0 (patch)
tree655acd79048a04d4f7b3dba81710d4118ef5829e /manual
parenta8110b727e508f7ddf34f940af622e6f95435201 (diff)
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Use gen-as-const.py to process .pysym files.
This patch eliminates the gen-py-const.awk variant of gen-as-const,
switching to use of gnu-as-const.py (with a new --python option) to
process .pysym files (i.e., to generate nptl_lock_constants.py), as
the syntax of those files is identical to that of .sym files.

Note that the generated nptl_lock_constants.py is *not* identical to
the version generated by the awk script.  Apart from the trivial
changes (comment referencing the new script, and output being sorted),
the constant FUTEX_WAITERS, PTHREAD_MUTEXATTR_FLAG_BITS,
PTHREAD_MUTEXATTR_FLAG_PSHARED and PTHREAD_MUTEX_PRIO_CEILING_MASK are
now output as positive rather than negative constants (on x86_64
anyway; maybe not necessarily on 32-bit systems):

< FUTEX_WAITERS = -2147483648
---
> FUTEX_WAITERS = 2147483648

< PTHREAD_MUTEXATTR_FLAG_BITS = -251662336
< PTHREAD_MUTEXATTR_FLAG_PSHARED = -2147483648
---
> PTHREAD_MUTEXATTR_FLAG_BITS = 4043304960
> PTHREAD_MUTEXATTR_FLAG_PSHARED = 2147483648

< PTHREAD_MUTEX_PRIO_CEILING_MASK = -524288
---
> PTHREAD_MUTEX_PRIO_CEILING_MASK = 4294443008

This is because gen-as-const has a cast of the constant value to long
int, which gen-py-const lacks.

I think the positive values are more logically correct, since the
constants in question are in fact unsigned in C.  But to reliably
produce gen-as-const.py output for constants that always (in C and
Python) reflects the signedness of values with the high bit of "long
int" set would mean more complicated logic needs to be used in
computing values.

The more correct positive values by themselves produce a failure of
nptl/test-mutexattr-printers, because masking with
~PTHREAD_MUTEXATTR_FLAG_BITS & ~PTHREAD_MUTEX_NO_ELISION_NP now leaves
a bit -1 << 32 in the Python value, resulting in a KeyError exception.
To avoid that, places masking with ~ of one of the constants in
question are changed to mask with 0xffffffff as well (this reflects
how ~ in Python applies to an infinite-precision integer whereas ~ in
C does not do any promotions beyond the width of int).

Tested for x86_64.

	* scripts/gen-as-const.py (main): Handle --python option.
	* scripts/gen-py-const.awk: Remove.
	* Makerules (py-const-script): Use gen-as-const.py.
	($(py-const)): Likewise.
	* nptl/nptl-printers.py (MutexPrinter.read_status_no_robust): Mask
	with 0xffffffff together with ~(PTHREAD_MUTEX_PRIO_CEILING_MASK).
	(MutexAttributesPrinter.read_values): Mask with 0xffffffff
	together with ~PTHREAD_MUTEXATTR_FLAG_BITS and
	~PTHREAD_MUTEX_NO_ELISION_NP.
	* manual/README.pretty-printers: Update reference to
	gen-py-const.awk.
Diffstat (limited to 'manual')
-rw-r--r--manual/README.pretty-printers2
1 files changed, 1 insertions, 1 deletions
diff --git a/manual/README.pretty-printers b/manual/README.pretty-printers
index 2522cb858d..a2ba89843c 100644
--- a/manual/README.pretty-printers
+++ b/manual/README.pretty-printers
@@ -104,7 +104,7 @@ Adding new pretty printers
 Adding new pretty printers to glibc requires following these steps:
 
 1. Identify which constants must be generated from C headers, and write the
-corresponding .pysym file.  See scripts/gen-py-const.awk for more information
+corresponding .pysym file.  See scripts/gen-as-const.py for more information
 on how this works.  The name of the .pysym file must be added to the
 'gen-py-const-headers' variable in your submodule's Makefile (without the .pysym
 extension).