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Avoid sharing cygheaps across Cygwin versions #48

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merged 2 commits into from
Jan 31, 2023
Merged

Avoid sharing cygheaps across Cygwin versions #48

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65ce633
Avoid sharing cygheaps across Cygwin versions
dscho Jan 30, 2023
4704d29
dumper: avoid linker problem when `libbfd` depends on `libsframe`
dscho Jan 31, 2023
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5 changes: 5 additions & 0 deletions winsup/configure.ac
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Expand Up @@ -110,6 +110,11 @@ AC_CHECK_LIB([bfd], [bfd_init], [true],

AM_CONDITIONAL(BUILD_DUMPER, [test "x$ac_cv_lib_bfd_bfd_init" = "xyes"])

AC_CHECK_LIB([sframe], [sframe_decode],
AC_MSG_NOTICE([Detected libsframe; Assuming that libbfd depends on it]), [true])

AM_CONDITIONAL(HAVE_LIBSFRAME, [test "x$ac_cv_lib_sframe_sframe_decode" = "xyes"])

AC_CONFIG_FILES([
Makefile
cygwin/Makefile
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2 changes: 1 addition & 1 deletion winsup/cygwin/dcrt0.cc
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Expand Up @@ -545,7 +545,7 @@ get_cygwin_startup_info ()
child_info *res = (child_info *) si.lpReserved2;

if (si.cbReserved2 < EXEC_MAGIC_SIZE || !res
|| res->intro != PROC_MAGIC_GENERIC || res->magic != CHILD_INFO_MAGIC)
|| res->intro != PROC_MAGIC_GENERIC || res->magic != (CHILD_INFO_MAGIC ^ CYGWIN_VERSION_DLL_COMBINED))
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I was surprised at first at the use of bitwise XOR here, as I would expect this to be a bitwise OR if these were flags. However, CYGWIN_VERSION_DLL_COMBINED is an integer with multiple bits (currently set to 3003006 to represent 3.3.6).

So this "magic" is very magical, it seems (and you do a similar update in sigproc.cc.

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But the commit message motivates this well, saying that we should use a new magic value whenever Git for Windows' version of MSYS2 is updated. (It's not accurate that only a new Git version would change this magic, but if two Git for Windows releases have the identical MSYS2 version, then they should be compatible still.)

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Indeed. The idea here is to have some kind of unique identifier that won't ever be shared between different MSYS2 runtime versions. Hence the XOR (because the OR would decrease the entropy).

{
strace.activate (false);
res = NULL;
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2 changes: 1 addition & 1 deletion winsup/cygwin/sigproc.cc
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Expand Up @@ -817,7 +817,7 @@ int child_info::retry_count = 0;
by fork/spawn/exec. */
child_info::child_info (unsigned in_cb, child_info_types chtype,
bool need_subproc_ready):
cb (in_cb), intro (PROC_MAGIC_GENERIC), magic (CHILD_INFO_MAGIC),
cb (in_cb), intro (PROC_MAGIC_GENERIC), magic (CHILD_INFO_MAGIC ^ CYGWIN_VERSION_DLL_COMBINED),
type (chtype), cygheap (::cygheap), cygheap_max (::cygheap_max),
flag (0), retry (child_info::retry_count), rd_proc_pipe (NULL),
wr_proc_pipe (NULL), sigmask (_my_tls.sigmask)
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4 changes: 4 additions & 0 deletions winsup/utils/Makefile.am
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Expand Up @@ -87,6 +87,10 @@ profiler_CXXFLAGS = -I$(srcdir) -idirafter ${top_srcdir}/cygwin -idirafter ${top
profiler_LDADD = $(LDADD) -lntdll
cygps_LDADD = $(LDADD) -lpsapi -lntdll

if HAVE_LIBSFRAME
dumper_LDADD += -lsframe
endif

if CROSS_BOOTSTRAP
SUBDIRS = mingw
endif