From 225bda24db9671e2087fda892f94141625836a40 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Tue, 4 May 2021 10:26:16 +0200 Subject: [PATCH] [gdb/guile] Don't allow libguile to change libgmp mem fns Since gdb commit 880ae75a2b7 "gdb delay guile initialization until gdbscm_finish_initialization" I'm running into: ... (gdb) print My_Var > 10.0^M free(): invalid pointer^M ERROR: GDB process no longer exists GDB process exited with wait status 5995 exp9 0 0 CHILDKILLED SIGABRT SIGABRT UNRESOLVED: gdb.ada/fixed_cmp.exp: gnat_encodings=all: print My_Var > 10.0 ... The problem is that both gdb and libguile try to set the libgmp memory functions, and since the gdb commit the ones from libguile are effective, which results in gdb freeing some memory in a way that is not compatible with the way that memory was actually allocated. The fact that libguile tries to set the libgmp memory functions is a bug which should be fixed starting version v3.0.6. Meanwhile, work around this in gdb by not allowing libguile to set the libgomp memory functions. Tested on x86_64-linux. gdb/ChangeLog: 2021-05-04 Tom de Vries PR guile/27806 * guile/guile.c (gdbscm_initialize): Don't let guile change libgmp memory functions. --- gdb/ChangeLog | 6 ++++++ gdb/guile/guile.c | 16 ++++++++++++++++ 2 files changed, 22 insertions(+) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 6ec6a701bfd..674817cc1b6 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2021-05-04 Tom de Vries + + PR guile/27806 + * guile/guile.c (gdbscm_initialize): Don't let guile change libgmp + memory functions. + 2021-04-30 Tom Tromey * dwarf2/read.c (dwarf2_initialize_objfile): Update. diff --git a/gdb/guile/guile.c b/gdb/guile/guile.c index bdf15cd498b..c6959f5b713 100644 --- a/gdb/guile/guile.c +++ b/gdb/guile/guile.c @@ -662,6 +662,22 @@ gdbscm_initialize (const struct extension_language_defn *extlang) { gdb::block_signals blocker; + /* There are libguile versions (f.i. v3.0.5) that by default call + mp_get_memory_functions during initialization to install custom + libgmp memory functions. This is considered a bug and should be + fixed starting v3.0.6. + Before gdb commit 880ae75a2b7 "gdb delay guile initialization until + gdbscm_finish_initialization", that bug had no effect for gdb, + because gdb subsequently called mp_get_memory_functions to install + its own custom functions in _initialize_gmp_utils. However, since + aforementioned gdb commit the initialization order is reversed, + allowing libguile to install a custom malloc that is incompatible + with the custom free as used in gmp-utils.c, resulting in a + "double free or corruption (out)" error. + Work around the libguile bug by disabling the installation of the + libgmp memory functions by guile initialization. */ + scm_install_gmp_memory_functions = 0; + /* scm_with_guile is the most portable way to initialize Guile. Plus we need to initialize the Guile support while in Guile mode (e.g., called from within a call to scm_with_guile). */ -- 2.30.2