From 01a97e1e03ca9600815d4cd48a18f438102d8104 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Mon, 26 May 2025 10:21:07 +0200
Subject: [PATCH 1/7] Implement `stabilize_sig_stack`

---
 winsup/cygwin/scripts/gendef | 67 ++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/winsup/cygwin/scripts/gendef b/winsup/cygwin/scripts/gendef
index 97ec62374d..03b6199999 100755
--- a/winsup/cygwin/scripts/gendef
+++ b/winsup/cygwin/scripts/gendef
@@ -399,7 +399,74 @@ _sigdelayed_end:
 
 	.seh_proc stabilize_sig_stack
 stabilize_sig_stack:
+	// prologue
+	stp	fp, lr, [sp, #-0x10]!		// save FP and LR registers
+	.seh_save_fplr_x+ 16
 	.seh_endprologue
+
+	ldr	x10, [x18, #0x8]		// keep thread local storage base address in x10
+
+	// try to acquire the lock
+	mov	w9, #1				// set up value for atomic exchange
+	ldr	x11, =_cygtls.stacklock		// load the symbol address/offset
+	add	x12, x10, x11			// calculate final address
+1:
+	ldaxr	w13, [x12]			// load with acquire semantics
+	stlxr	w14, w9, [x12]			// store with release semantics
+	cbnz	w14, 1b				// if store failed, retry
+	cbz	w13, 2f				// if lock was acquired, continue
+	yield					// yield to allow other threads to run
+	b	1b				// retry acquiring the lock
+2:
+	// lock acquired, increment incyg counter
+	ldr	x11, =_cygtls.incyg		// load the symbol address/offset
+	add	x12, x10, x11			// calculate final address
+	ldr	w9, [x12]			// load current value of incyg counter
+	add	w9, w9, #1			// increment incyg counter
+	str	w9, [x12]			// store incremented value back
+
+	// check if there is a current signal to handle 
+	ldr	x11, =_cygtls.current_sig	// load the symbol address/offset
+	ldr	w9, [x10, x11]			// load current value of current_sig
+	cbz	w9, 3f				// if no current signal, jump to cleanup
+
+	// release lock before calling signal handler
+	ldr	x11, =_cygtls.stacklock		// load the symbol address/offset
+	add	x12, x10, x11			// calculate final address
+	ldr	w9, [x12]			// load current value of stacklock counter
+	sub	w9, w9, #1			// decrement stacklock counter
+	stlr	w9, [x12]			// store with release semantics
+
+	// prepare arguments and call signal handler
+	ldr	x0, =_cygtls.start_offset	// load the symbol address/offset
+	add	x0, x10, x0			// calculate final address
+	bl	_ZN7_cygtls19call_signal_handlerEv
+	ldr	x10, [x18, #0x8]		// restore x10 that may have been modified by the call
+
+	// decrement incyg counter
+	ldr	x11, =_cygtls.incyg		// load the symbol address/offset
+	add	x12, x10, x11			// calculate final address
+	ldr	w9, [x12]			// load current value of incyg counter
+	sub	w9, w9, #1			// decrement incyg counter
+	str	w9, [x12]			// store decremented value back
+
+	// go to the beginning to handle another signal
+	b	1b
+3:
+	// no signal to handle, decrement incyg counter
+	ldr	x11, =_cygtls.incyg		// load the symbol address/offset
+	add	x12, x10, x11			// calculate final address
+	ldr	w9, [x12]			// load current value of incyg counter
+	sub	w9, w9, #1			// decrement incyg counter
+	str	w9, [x12]			// store decremented value back
+
+	mov	x0, x10				// return TLS address in x0 (return value)
+
+	// epilogue
+	.seh_startepilogue
+	ldp	fp, lr, [sp], #0x10
+	.seh_save_fplr_x+ 16
+	.seh_endepilogue
 	ret
 	.seh_endproc
 EOF

From 287ceb21c31ec23f8833a6816789616ddd36416c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Mon, 26 May 2025 17:00:04 +0200
Subject: [PATCH 2/7] Implement `setjmp`

---
 winsup/cygwin/scripts/gendef | 47 +++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/scripts/gendef b/winsup/cygwin/scripts/gendef
index 03b6199999..a4415970ff 100755
--- a/winsup/cygwin/scripts/gendef
+++ b/winsup/cygwin/scripts/gendef
@@ -622,8 +622,53 @@ sigsetjmp:
 	.globl  setjmp
 	.seh_proc setjmp
 setjmp:
+	// prologue
+	stp	fp, lr, [sp, #-0x10]!		// save FP and LR registers
 	.seh_endprologue
-	mov x0, 0
+
+	// save callee-saved registers from jump buffer
+	stp	x19, x20, [x0, #0x08]		// save x19 and x20
+	stp	x21, x22, [x0, #0x18]		// save x21 and x22
+	stp	x23, x24, [x0, #0x28]		// save x23 and x24
+	stp	x25, x26, [x0, #0x38]		// save x25 and x26
+	stp	x27, x28, [x0, #0x48]		// save x27 and x28
+	stp	fp, lr, [x0, #0x58]		// save x29 (frame pointer) and x30 (link register)
+	mov	x1, sp				// get the current stack pointer
+	str	x1, [x0, #0x68]			// save SP
+	mrs	x1, fpcr			// get floating-point control register
+	str	x1, [x0, #0x70]			// save FPCR
+	mrs	x1, fpsr			// get floating-point status register
+	str	x1, [x0, #0x78]			// save FPSR
+
+	// save floating-point registers (d8-d15)
+	stp	d8, d9, [x0, #0x80]
+	stp	d10, d11, [x0, #0x90]
+	stp	d12, d13, [x0, #0xA0]
+	stp	d14, d15, [x0, #0xB0]
+
+	// save TLS stack pointer
+	ldr	x1, [sp]
+	str	x1, [x0, #0xB8]
+
+	bl	stabilize_sig_stack		// call stabilize_sig_stack (returns TLS in x0)
+
+	// store the stack pointer to ...
+	ldr	x2, =_cygtls.stackptr
+	add	x2, x0, x2
+	ldr	x3, [x2]
+	// TODO: Save the value somewhere.
+
+	// decrement the stack lock
+	ldr	x2, =_cygtls.stacklock
+	add	x2, x0, x2
+	ldr	w3, [x2]
+	sub	w3, w3, #1
+	str	w3, [x2]
+
+	mov	w0, #0				// return 0
+
+	// epilogue
+	ldp	fp, lr, [sp], #0x10		// restore saved FP and LR registers
 	ret
 	.seh_endproc
 

From 8c9821fbcc7fa9538f23de65638ab36356d2b17e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Mon, 26 May 2025 17:00:45 +0200
Subject: [PATCH 3/7] Implement `longjmp`

---
 winsup/cygwin/scripts/gendef | 60 ++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/winsup/cygwin/scripts/gendef b/winsup/cygwin/scripts/gendef
index a4415970ff..eda373e085 100755
--- a/winsup/cygwin/scripts/gendef
+++ b/winsup/cygwin/scripts/gendef
@@ -682,7 +682,67 @@ siglongjmp:
 	.globl  longjmp
 	.seh_proc longjmp
 longjmp:
+	// prologue
+	stp	fp, lr, [sp, #-0x20]!		// save FP and LR registers, allocate additional 16 bytes for function arguments
+	stp	x0, x1, [sp, #0x10]		// save function arguments (jump buffer and return value)
+	mov	fp, sp				// establishing frame chain
 	.seh_endprologue
+1:
+	bl	stabilize_sig_stack		// call stabilize_sig_stack which returns TLS pointer in x0
+	ldr	x2, [sp, #0x10]			// get jump buffer pointer from stack
+	ldr	x10, [x2]			// get old signal stack from jump buffer
+
+	// restore stack pointer in TLS
+	ldr	x11, =_cygtls.stackptr
+	add	x11, x0, x11
+	str	x10, [x11]
+
+	// release lock by decrementing counter
+	ldr	x11, =_cygtls.stacklock
+	add	x11, x0, x11
+	ldr	w12, [x11]
+	sub	w12, w12, #1
+	str	w12, [x11]
+
+	// we're not in cygwin anymore, clear "in cygwin" flag
+	ldr	x11, =_cygtls.incyg
+	add	x11, x0, x11
+	mov	w12, #0
+	str	w12, [x11]
+
+	// get saved return value before SP is restored
+	ldr	x0, [sp, #0x10]
+
+	// restore callee-saved registers from jump buffer
+	ldp	x19, x20, [x2, #0x08]		// restore x19, x20
+	ldp	x21, x22, [x2, #0x18]		// restore x21, x22
+	ldp	x23, x24, [x2, #0x28]		// restore x23, x24
+	ldp	x25, x26, [x2, #0x38]		// restore x25, x26
+	ldp	x27, x28, [x2, #0x48]		// restore x27, x28
+	ldp	fp, lr, [x2, #0x58]		// restore x29 (frame pointer) and x30 (link register)
+	ldr	x10, [x2, #0x68]		// get saved stack pointer
+	mov	sp, x10				// restore stack pointer
+	ldr	x10, [x2, #0x70]		// load floating-point control register
+	msr	fpcr, x10			// restore FPCR
+	ldr	x10, [x2, #0x78]		// load floating-point status register
+	msr	fpsr, x10			// restore FPSR
+
+	// restore floating-point registers (d8-d15)
+	ldp	d8, d9, [x2, #0x80]
+	ldp	d10, d11, [x2, #0x90]
+	ldp	d12, d13, [x2, #0xA0]
+	ldp	d14, d15, [x2, #0xB0]
+
+	// restore TLS stack pointer
+	ldr	x1, [x0, #0xB8]
+	str	x1, [sp]
+
+	// ensure return value is non-zero (C standard requirement)
+	cbnz	x0, 0f
+	mov	x0, #1
+0:
+	// epilogue
+	add	sp, sp, #0x10			// FP and LR are already restored, just restore SP as it would be popped
 	ret
 	.seh_endproc
 EOF

From a157c660cb045abc7be19f7ce203e7810b5d4d40 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Wed, 16 Apr 2025 14:09:14 +0200
Subject: [PATCH 4/7] WIP: Implement `_sigfe_maybe`, `_sigfe` and `_sigbe`

---
 winsup/cygwin/scripts/gendef | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/scripts/gendef b/winsup/cygwin/scripts/gendef
index eda373e085..0d0fde661a 100755
--- a/winsup/cygwin/scripts/gendef
+++ b/winsup/cygwin/scripts/gendef
@@ -370,14 +370,15 @@ EOF
 	.seh_proc _sigfe_maybe
 _sigfe_maybe:					# stack is aligned on entry!
 	.seh_endprologue
+	ldr x10, [x18, #0x8]
 0:	ret
 	.seh_endproc
 
 	.seh_proc _sigfe
 _sigfe:						# stack is aligned on entry!
 	.seh_endprologue
-	ldr x9, [sp], #16
-	br x9
+	ldr	x10, [sp], #0x10
+	br	x10
 	.seh_endproc
 
 	.global _sigbe
@@ -385,6 +386,7 @@ _sigfe:						# stack is aligned on entry!
 _sigbe:						# return here after cygwin syscall
 						# stack is aligned on entry!
 	.seh_endprologue
+	ret
 	.seh_endproc
 
 	.global	sigdelayed

From d7bf92cdcbdd476956b8b47400b26c796d4b30fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Wed, 16 Apr 2025 14:10:06 +0200
Subject: [PATCH 5/7] WIP: Implement `sigsetjmp`

---
 winsup/cygwin/scripts/gendef | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/scripts/gendef b/winsup/cygwin/scripts/gendef
index 0d0fde661a..900508a242 100755
--- a/winsup/cygwin/scripts/gendef
+++ b/winsup/cygwin/scripts/gendef
@@ -616,8 +616,16 @@ EOF
 	.globl	sigsetjmp
 	.seh_proc sigsetjmp
 sigsetjmp:
+	// prologue
+	stp	fp, lr, [sp, #-0x10]!		// save FP and LR registers
+	mov	fp, sp				// set FP to current SP
+	sub	sp, sp, #0x20			// allocate 32 bytes on stack
 	.seh_endprologue
-	mov x0, 0
+
+	bl setjmp
+
+	// epilogue
+	ldp	fp, lr, [sp], #0x10		// restore saved FP and LR registers
 	ret
 	.seh_endproc
 

From c71723f221e8f1cf9ac96961a4aaa80bb5058e7a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Wed, 16 Apr 2025 14:09:44 +0200
Subject: [PATCH 6/7] WIP: Implement `siglongjmp`

---
 winsup/cygwin/scripts/gendef | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/winsup/cygwin/scripts/gendef b/winsup/cygwin/scripts/gendef
index 900508a242..07db143b39 100755
--- a/winsup/cygwin/scripts/gendef
+++ b/winsup/cygwin/scripts/gendef
@@ -685,7 +685,16 @@ setjmp:
 	.globl	siglongjmp
 	.seh_proc siglongjmp
 siglongjmp:
+	// prologue
+	stp	fp, lr, [sp, #-0x10]!		// save FP and LR registers
+	mov	fp, sp				// set FP to current SP
+	sub	sp, sp, #32			// allocate 32 bytes on stack
 	.seh_endprologue
+
+	bl longjmp
+
+	// epilogue
+	ldp	fp, lr, [sp], #0x10		// restore saved FP and LR registers
 	ret
 	.seh_endproc
 

From 2e038205f916fa84c4bc87afef62fc637876c0f1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Wed, 16 Apr 2025 13:00:26 +0200
Subject: [PATCH 7/7] Disable optimizations for easier debugging

---
 Makefile.in                      | 4 ++--
 Makefile.tpl                     | 4 ++--
 config/acinclude.m4              | 4 ++--
 configure                        | 8 ++++----
 configure.ac                     | 4 ++--
 libgloss/config/default.mh       | 2 +-
 libgloss/config/dos.mh           | 2 +-
 libgloss/config/ppc.mh           | 2 +-
 libgloss/configure               | 2 +-
 libtool.m4                       | 2 +-
 newlib/configure                 | 2 +-
 winsup/cygwin/aarch64/fastcwd.cc | 8 ++++----
 winsup/cygwin/syscalls.cc        | 2 +-
 13 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index 25f82d37f1..32885d0433 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -364,7 +364,7 @@ BUILD_PREFIX_1 = @BUILD_PREFIX_1@
 
 # Flags to pass to stage2 and later makes.  They are defined
 # here so that they can be overridden by Makefile fragments.
-BOOT_CFLAGS= -g -O2
+BOOT_CFLAGS= -g -Og
 BOOT_LDFLAGS=
 BOOT_ADAFLAGS= -gnatpg
 
@@ -584,7 +584,7 @@ CXXFLAGS_FOR_TARGET = @CXXFLAGS_FOR_TARGET@
 LIBCFLAGS_FOR_TARGET = $(CFLAGS_FOR_TARGET)
 LIBCXXFLAGS_FOR_TARGET = $(CXXFLAGS_FOR_TARGET) -fno-implicit-templates
 LDFLAGS_FOR_TARGET = @LDFLAGS_FOR_TARGET@
-GOCFLAGS_FOR_TARGET = -O2 -g
+GOCFLAGS_FOR_TARGET = -Og -g
 
 FLAGS_FOR_TARGET = @FLAGS_FOR_TARGET@
 SYSROOT_CFLAGS_FOR_TARGET = @SYSROOT_CFLAGS_FOR_TARGET@
diff --git a/Makefile.tpl b/Makefile.tpl
index 21e12e897c..8c3e0cebc5 100644
--- a/Makefile.tpl
+++ b/Makefile.tpl
@@ -367,7 +367,7 @@ BUILD_PREFIX_1 = @BUILD_PREFIX_1@
 
 # Flags to pass to stage2 and later makes.  They are defined
 # here so that they can be overridden by Makefile fragments.
-BOOT_CFLAGS= -g -O2
+BOOT_CFLAGS= -g -Og
 BOOT_LDFLAGS=
 BOOT_ADAFLAGS= -gnatpg
 
@@ -517,7 +517,7 @@ CXXFLAGS_FOR_TARGET = @CXXFLAGS_FOR_TARGET@
 LIBCFLAGS_FOR_TARGET = $(CFLAGS_FOR_TARGET)
 LIBCXXFLAGS_FOR_TARGET = $(CXXFLAGS_FOR_TARGET) -fno-implicit-templates
 LDFLAGS_FOR_TARGET = @LDFLAGS_FOR_TARGET@
-GOCFLAGS_FOR_TARGET = -O2 -g
+GOCFLAGS_FOR_TARGET = -Og -g
 
 FLAGS_FOR_TARGET = @FLAGS_FOR_TARGET@
 SYSROOT_CFLAGS_FOR_TARGET = @SYSROOT_CFLAGS_FOR_TARGET@
diff --git a/config/acinclude.m4 b/config/acinclude.m4
index 8242b2c7a8..5760acac82 100644
--- a/config/acinclude.m4
+++ b/config/acinclude.m4
@@ -24,7 +24,7 @@ dnl normal versions of a library), tasteless as that idea is.
   if test "$ac_test_CXXFLAGS" = set; then
     CXXFLAGS="$ac_save_CXXFLAGS"
   elif test $ac_cv_prog_cxx_g = yes; then
-    CXXFLAGS="-g -O2"
+    CXXFLAGS="-g -Og"
   else
     CXXFLAGS="-O2"
   fi
@@ -121,7 +121,7 @@ dnl normal versions of a library), tasteless as that idea is.
   if test "$ac_test_CFLAGS" = set; then
     CFLAGS="$ac_save_CFLAGS"
   elif test $ac_cv_prog_cc_g = yes; then
-    CFLAGS="-g -O2"
+    CFLAGS="-g -Og"
   else
     CFLAGS="-O2"
   fi
diff --git a/configure b/configure
index 9477153056..4164e33ff3 100755
--- a/configure
+++ b/configure
@@ -4800,7 +4800,7 @@ if test "$ac_test_CFLAGS" = set; then
   CFLAGS=$ac_save_CFLAGS
 elif test $ac_cv_prog_cc_g = yes; then
   if test "$GCC" = yes; then
-    CFLAGS="-g -O2"
+    CFLAGS="-g -Og"
   else
     CFLAGS="-g"
   fi
@@ -5147,7 +5147,7 @@ if test "$ac_test_CXXFLAGS" = set; then
   CXXFLAGS=$ac_save_CXXFLAGS
 elif test $ac_cv_prog_cxx_g = yes; then
   if test "$GXX" = yes; then
-    CXXFLAGS="-g -O2"
+    CXXFLAGS="-g -Og"
   else
     CXXFLAGS="-g"
   fi
@@ -6853,7 +6853,7 @@ fi
 # CFLAGS_FOR_TARGET and CXXFLAGS_FOR_TARGET.
 if test "x$CFLAGS_FOR_TARGET" = x; then
   if test "x${is_cross_compiler}" = xyes; then
-    CFLAGS_FOR_TARGET="-g -O2"
+    CFLAGS_FOR_TARGET="-g -Og"
   else
     CFLAGS_FOR_TARGET=$CFLAGS
     case " $CFLAGS " in
@@ -6870,7 +6870,7 @@ fi
 
 if test "x$CXXFLAGS_FOR_TARGET" = x; then
   if test "x${is_cross_compiler}" = xyes; then
-    CXXFLAGS_FOR_TARGET="-g -O2"
+    CXXFLAGS_FOR_TARGET="-g -Og"
   else
     CXXFLAGS_FOR_TARGET=$CXXFLAGS
     case " $CXXFLAGS " in
diff --git a/configure.ac b/configure.ac
index 7e8a6b1c61..48b830f37d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2381,7 +2381,7 @@ AC_SUBST(DEBUG_PREFIX_CFLAGS_FOR_TARGET)
 # CFLAGS_FOR_TARGET and CXXFLAGS_FOR_TARGET.
 if test "x$CFLAGS_FOR_TARGET" = x; then
   if test "x${is_cross_compiler}" = xyes; then
-    CFLAGS_FOR_TARGET="-g -O2"
+    CFLAGS_FOR_TARGET="-g -Og"
   else
     CFLAGS_FOR_TARGET=$CFLAGS
     case " $CFLAGS " in
@@ -2398,7 +2398,7 @@ AC_SUBST(CFLAGS_FOR_TARGET)
 
 if test "x$CXXFLAGS_FOR_TARGET" = x; then
   if test "x${is_cross_compiler}" = xyes; then
-    CXXFLAGS_FOR_TARGET="-g -O2"
+    CXXFLAGS_FOR_TARGET="-g -Og"
   else
     CXXFLAGS_FOR_TARGET=$CXXFLAGS
     case " $CXXFLAGS " in
diff --git a/libgloss/config/default.mh b/libgloss/config/default.mh
index 64dc02f05c..df0f1a96f6 100644
--- a/libgloss/config/default.mh
+++ b/libgloss/config/default.mh
@@ -4,7 +4,7 @@ NEWLIB_LDFLAGS = `if [ -d ${objroot}/newlib ]; then echo -B${objroot}/newlib/ -L
 INCLUDES = -I. -I$(srcdir)/.. -I$(objdir)/.. -idirafter $(srcroot)/include
 # Note that when building the library, ${MULTILIB} is not the way multilib
 # options are passed; they're passed in $(CFLAGS).
-CFLAGS_FOR_TARGET = -O2 -g ${MULTILIB} ${INCLUDES} ${NEWLIB_CFLAGS}
+CFLAGS_FOR_TARGET = -Og -g ${MULTILIB} ${INCLUDES} ${NEWLIB_CFLAGS}
 LDFLAGS_FOR_TARGET = ${MULTILIB} ${NEWLIB_LDFLAGS}
 AR_FLAGS = rc
 
diff --git a/libgloss/config/dos.mh b/libgloss/config/dos.mh
index c5874cb424..0046963eba 100644
--- a/libgloss/config/dos.mh
+++ b/libgloss/config/dos.mh
@@ -4,7 +4,7 @@ NEWLIB_LDFLAGS = `if [ -d ${objroot}/newlib ]; then echo -B${objroot}/newlib/; f
 INCLUDES = -I.
 # Note that when building the library, ${MULTILIB} is not the way multilib
 # options are passed; they're passed in $(CFLAGS).
-CFLAGS_FOR_TARGET = -O2 -g ${MULTILIB} ${INCLUDES} ${NEWLIB_CFLAGS}
+CFLAGS_FOR_TARGET = -Og -g ${MULTILIB} ${INCLUDES} ${NEWLIB_CFLAGS}
 LDFLAGS_FOR_TARGET = ${MULTILIB} ${NEWLIB_LDFLAGS}
 ARFLAGS_FOR_TARGET = qc
 
diff --git a/libgloss/config/ppc.mh b/libgloss/config/ppc.mh
index d1bfd7588e..d8a957360a 100644
--- a/libgloss/config/ppc.mh
+++ b/libgloss/config/ppc.mh
@@ -8,7 +8,7 @@ CFLAGS_MRELOCATABLE = -mrelocatable-lib -mno-eabi
 INCLUDES = -I. -I$(srcdir)/.. -I$(objdir)/..
 # Note that when building the library, ${MULTILIB} is not the way multilib
 # options are passed; they're passed in $(CFLAGS).
-CFLAGS_FOR_TARGET = -O2 -g ${MULTILIB} ${INCLUDES} ${NEWLIB_CFLAGS}
+CFLAGS_FOR_TARGET = -Og -g ${MULTILIB} ${INCLUDES} ${NEWLIB_CFLAGS}
 LDFLAGS_FOR_TARGET = ${MULTILIB} ${NEWLIB_LDFLAGS}
 AR_FLAGS = qc
 
diff --git a/libgloss/configure b/libgloss/configure
index 3eb4c27402..dd5d52d9a3 100755
--- a/libgloss/configure
+++ b/libgloss/configure
@@ -4077,7 +4077,7 @@ if test "$ac_test_CFLAGS" = set; then
   CFLAGS=$ac_save_CFLAGS
 elif test $ac_cv_prog_cc_g = yes; then
   if test "$GCC" = yes; then
-    CFLAGS="-g -O2"
+    CFLAGS="-g -Og"
   else
     CFLAGS="-g"
   fi
diff --git a/libtool.m4 b/libtool.m4
index a216bb14e9..3c4b0be976 100644
--- a/libtool.m4
+++ b/libtool.m4
@@ -7074,7 +7074,7 @@ AC_DEFUN([LT_PROG_GCJ],
 [m4_ifdef([AC_PROG_GCJ], [AC_PROG_GCJ],
   [m4_ifdef([A][M_PROG_GCJ], [A][M_PROG_GCJ],
     [AC_CHECK_TOOL(GCJ, gcj,)
-      test "x${GCJFLAGS+set}" = xset || GCJFLAGS="-g -O2"
+      test "x${GCJFLAGS+set}" = xset || GCJFLAGS="-g -Og"
       AC_SUBST(GCJFLAGS)])])[]dnl
 ])
 
diff --git a/newlib/configure b/newlib/configure
index 004a4a9975..3462881339 100755
--- a/newlib/configure
+++ b/newlib/configure
@@ -4029,7 +4029,7 @@ if test "$ac_test_CFLAGS" = set; then
   CFLAGS=$ac_save_CFLAGS
 elif test $ac_cv_prog_cc_g = yes; then
   if test "$GCC" = yes; then
-    CFLAGS="-g -O2"
+    CFLAGS="-g -Og"
   else
     CFLAGS="-g"
   fi
diff --git a/winsup/cygwin/aarch64/fastcwd.cc b/winsup/cygwin/aarch64/fastcwd.cc
index 17ce6bbf3d..b95c3dba6b 100644
--- a/winsup/cygwin/aarch64/fastcwd.cc
+++ b/winsup/cygwin/aarch64/fastcwd.cc
@@ -128,8 +128,8 @@ find_fast_cwd_pointer_aarch64 ()
   start = pc = (const uint32_t *) use_cwd;
 
   const uint32_t *ldrpc = NULL;
-  uint32_t ldroffset, ldrsz;
-  uint32_t ldrrn, ldrrd;
+  uint32_t ldroffset = 0, ldrsz = 0;
+  uint32_t ldrrn = 0, ldrrd = 0;
 
   /* find the ldr (immediate unsigned offset) for RtlpCurDirRef */
   for (; pc < start + 20 && !IS_INSN (pc, ret) && !IS_INSN (pc, b); pc++)
@@ -163,8 +163,8 @@ find_fast_cwd_pointer_aarch64 ()
       if (IS_INSN (pc, bl) && extract_bl_target (pc) == ent_crit)
 	break;
     }
-  uint32_t addoffset;
-  uint32_t addrn;
+  uint32_t addoffset = 0;
+  uint32_t addrn = 0;
   for (; pc >= start; pc--)
     {
       if (IS_INSN (pc, add) && (*pc & 0x1F) == 0)
diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index d6a2c2d3b3..8742829a1b 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -1595,7 +1595,7 @@ static int
 posix_getdents_lseek (cygheap_fdget &cfd, off_t pos, int dir)
 {
   long cur = cfd->telldir (cfd->getdents_dir ());
-  long abs_pos;
+  long abs_pos = 0;
 
   switch (dir)
     {