From 85aecf463c1d5c7167152d0af8f7e32a7ec98540 Mon Sep 17 00:00:00 2001
From: Tim Ruffing <crypto@timruffing.de>
Date: Tue, 27 Jun 2023 15:04:13 +0200
Subject: [PATCH 1/5] build: Use dllexport also for Cygwin builds
As recommended by https://gcc.gnu.org/wiki/Visibility
---
include/secp256k1.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/secp256k1.h b/include/secp256k1.h
index 01d18cff09..56e9b580bf 100644
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -135,7 +135,7 @@ typedef int (*secp256k1_nonce_function)(
/* Symbol visibility. See https://gcc.gnu.org/wiki/Visibility */
/* DLL_EXPORT is defined internally for shared builds */
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__CYGWIN__)
# ifdef SECP256K1_BUILD
# ifdef DLL_EXPORT
# define SECP256K1_API __declspec (dllexport)
From 297c85ac06fdc612049a0c6236b98850eeb56acd Mon Sep 17 00:00:00 2001
From: Tim Ruffing <crypto@timruffing.de>
Date: Tue, 27 Jun 2023 15:20:06 +0200
Subject: [PATCH 2/5] build: Add #ifdefs for requesting import as DLL vs static
explicitly
---
include/secp256k1.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/include/secp256k1.h b/include/secp256k1.h
index 56e9b580bf..62ec74e99c 100644
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -136,11 +136,20 @@ typedef int (*secp256k1_nonce_function)(
/* Symbol visibility. See https://gcc.gnu.org/wiki/Visibility */
/* DLL_EXPORT is defined internally for shared builds */
#if defined(_WIN32) || defined(__CYGWIN__)
+# if defined(SECP256K1_STATICLIB) && defined(SECP256K1_DLL)
+# error "At most one of SECP256K1_STATICLIB and SECP256K1_DLL must be defined."
+# endif
# ifdef SECP256K1_BUILD
# ifdef DLL_EXPORT
# define SECP256K1_API __declspec (dllexport)
# define SECP256K1_API_VAR extern __declspec (dllexport)
# endif
+# elif defined(SECP256K1_STATICLIB)
+# define SECP256K1_API
+# define SECP256K1_API_VAR extern
+# elif defined(SECP256K1_DLL)
+# define SECP256K1_API __declspec (dllimport)
+# define SECP256K1_API_VAR extern __declspec (dllimport)
# elif defined _MSC_VER
# define SECP256K1_API
# define SECP256K1_API_VAR extern __declspec (dllimport)
From d2117f08b27a1b1451733e7b97695f0ccd272ac4 Mon Sep 17 00:00:00 2001
From: Tim Ruffing <crypto@timruffing.de>
Date: Tue, 27 Jun 2023 15:22:44 +0200
Subject: [PATCH 3/5] build: Add extensive docs on visibility issues
---
include/secp256k1.h | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)
diff --git a/include/secp256k1.h b/include/secp256k1.h
index 62ec74e99c..4e0c04ca21 100644
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -133,36 +133,56 @@ typedef int (*secp256k1_nonce_function)(
# define SECP256K1_NO_BUILD
#endif
-/* Symbol visibility. See https://gcc.gnu.org/wiki/Visibility */
-/* DLL_EXPORT is defined internally for shared builds */
+/* Symbol visibility. */
#if defined(_WIN32) || defined(__CYGWIN__)
# if defined(SECP256K1_STATICLIB) && defined(SECP256K1_DLL)
# error "At most one of SECP256K1_STATICLIB and SECP256K1_DLL must be defined."
# endif
-# ifdef SECP256K1_BUILD
-# ifdef DLL_EXPORT
+ /* GCC for Windows (e.g., MinGW) and for Cygwin accept the __declspec syntax
+ * for MSVC compatibility. A __declspec declaration implies (but is not
+ * exactly equivalent to) __attribute__ ((visibility("default"))), and so we
+ * actually want __declspec even on GCC, see "Microsoft Windows Function
+ * Attributes" in the GCC manual and the recommendations in
+ * https://gcc.gnu.org/wiki/Visibility. */
+# if defined(SECP256K1_BUILD)
+# if defined(DLL_EXPORT)
+ /* Building libsecp256k1 as a DLL. (DLL_EXPORT is a libtool convention.) */
# define SECP256K1_API __declspec (dllexport)
# define SECP256K1_API_VAR extern __declspec (dllexport)
# endif
# elif defined(SECP256K1_STATICLIB)
+ /* Linking against static libsecp256k1 requested explicitly. */
# define SECP256K1_API
# define SECP256K1_API_VAR extern
# elif defined(SECP256K1_DLL)
+ /* Linking against a libsecp256k1 DLL requested explicitly. */
# define SECP256K1_API __declspec (dllimport)
# define SECP256K1_API_VAR extern __declspec (dllimport)
-# elif defined _MSC_VER
+# elif defined(_MSC_VER)
+ /* No method requested explicitly. The following works on MSVC for both
+ * static and dynamic linking, as long as if at least one function is
+ * imported (i.e., not only variables are imported), which should be the case
+ * for any meaningful program that uses the libsecp256k1 API. The drawback of
+ * the following is that it may provoke linker warnings LNK4217 and LNK4286.
+ * See "Windows DLLs" in the libtool manual. */
# define SECP256K1_API
# define SECP256K1_API_VAR extern __declspec (dllimport)
-# elif defined DLL_EXPORT
+# elif defined(DLL_EXPORT)
+ /* No method requested explicitly and we're not on MSVC. We make an educated
+ * guess based on libtool's DLL_EXPORT convention: If the importing program
+ * is itself a DLL, then it is likely that it also wants to consume
+ * libsecp256k1 as a DLL. See "Windows DLLs" in the libtool manual. */
# define SECP256K1_API __declspec (dllimport)
# define SECP256K1_API_VAR extern __declspec (dllimport)
# endif
#endif
#ifndef SECP256K1_API
# if defined(__GNUC__) && (__GNUC__ >= 4) && defined(SECP256K1_BUILD)
+ /* Building libsecp256k1 on non-Windows using GCC or compatible. */
# define SECP256K1_API __attribute__ ((visibility ("default")))
# define SECP256K1_API_VAR extern __attribute__ ((visibility ("default")))
# else
+ /* All cases not captured above. */
# define SECP256K1_API
# define SECP256K1_API_VAR extern
# endif
From 69918b823f8679c59a4eae78b191c041758a03bf Mon Sep 17 00:00:00 2001
From: Tim Ruffing <crypto@timruffing.de>
Date: Wed, 28 Jun 2023 11:29:30 +0200
Subject: [PATCH 4/5] build: Accept SECP256K1_DLL in addition to DLL_EXPORT in
lib builds
Addresses one item in #1235.
---
include/secp256k1.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/secp256k1.h b/include/secp256k1.h
index 4e0c04ca21..cd9f3766d2 100644
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -145,7 +145,7 @@ typedef int (*secp256k1_nonce_function)(
* Attributes" in the GCC manual and the recommendations in
* https://gcc.gnu.org/wiki/Visibility. */
# if defined(SECP256K1_BUILD)
-# if defined(DLL_EXPORT)
+# if defined(SECP256K1_DLL) || defined(DLL_EXPORT)
/* Building libsecp256k1 as a DLL. (DLL_EXPORT is a libtool convention.) */
# define SECP256K1_API __declspec (dllexport)
# define SECP256K1_API_VAR extern __declspec (dllexport)
From 5267c8b5ad2b1fb3879074ac6a5b01a250945685 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Tue, 13 Jun 2023 13:49:19 +0100
Subject: [PATCH 5/5] build: Use `SECP256K1_STATICLIB` macro instead of warning
suppressions
This makes uses of the freshly introduced `SECP256K1_STATICLIB` macro
instead of ignoring MSVC linker warnings LNK4217 and LNK4286.
Co-authored-by: Tim Ruffing <crypto@timruffing.de>
---
Makefile.am | 6 +++---
configure.ac | 6 ------
examples/CMakeLists.txt | 2 +-
3 files changed, 4 insertions(+), 10 deletions(-)
diff --git a/Makefile.am b/Makefile.am
index ee14ac4509..a30bad81f0 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -153,7 +153,7 @@ endif
if USE_EXAMPLES
noinst_PROGRAMS += ecdsa_example
ecdsa_example_SOURCES = examples/ecdsa.c
-ecdsa_example_CPPFLAGS = -I$(top_srcdir)/include
+ecdsa_example_CPPFLAGS = -I$(top_srcdir)/include -DSECP256K1_STATICLIB
ecdsa_example_LDADD = libsecp256k1.la
ecdsa_example_LDFLAGS = -static
if BUILD_WINDOWS
@@ -163,7 +163,7 @@ TESTS += ecdsa_example
if ENABLE_MODULE_ECDH
noinst_PROGRAMS += ecdh_example
ecdh_example_SOURCES = examples/ecdh.c
-ecdh_example_CPPFLAGS = -I$(top_srcdir)/include
+ecdh_example_CPPFLAGS = -I$(top_srcdir)/include -DSECP256K1_STATICLIB
ecdh_example_LDADD = libsecp256k1.la
ecdh_example_LDFLAGS = -static
if BUILD_WINDOWS
@@ -174,7 +174,7 @@ endif
if ENABLE_MODULE_SCHNORRSIG
noinst_PROGRAMS += schnorr_example
schnorr_example_SOURCES = examples/schnorr.c
-schnorr_example_CPPFLAGS = -I$(top_srcdir)/include
+schnorr_example_CPPFLAGS = -I$(top_srcdir)/include -DSECP256K1_STATICLIB
schnorr_example_LDADD = libsecp256k1.la
schnorr_example_LDFLAGS = -static
if BUILD_WINDOWS
diff --git a/configure.ac b/configure.ac
index 82cf95132d..a502d1304a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -127,12 +127,6 @@ AC_DEFUN([SECP_TRY_APPEND_DEFAULT_CFLAGS], [
SECP_TRY_APPEND_CFLAGS([-wd4267], $1) # Disable warning C4267 "'var' : conversion from 'size_t' to 'type', possible loss of data".
# Eliminate deprecation warnings for the older, less secure functions.
CPPFLAGS="-D_CRT_SECURE_NO_WARNINGS $CPPFLAGS"
- # We pass -ignore:4217 to the MSVC linker to suppress warning 4217 when
- # importing variables from a statically linked secp256k1.
- # (See the libtool manual, section "Windows DLLs" for background.)
- # Unfortunately, libtool tries to be too clever and strips "-Xlinker arg"
- # into "arg", so this will be " -Xlinker -ignore:4217" after stripping.
- LDFLAGS="-Xlinker -Xlinker -Xlinker -ignore:4217 $LDFLAGS"
fi
])
SECP_TRY_APPEND_DEFAULT_CFLAGS(SECP_CFLAGS)
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index e095b7f84f..a314c1787c 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -7,7 +7,7 @@ target_link_libraries(example INTERFACE
$<$<PLATFORM_ID:Windows>:bcrypt>
)
if(NOT BUILD_SHARED_LIBS AND MSVC)
- target_link_options(example INTERFACE /IGNORE:4217)
+ target_compile_definitions(example INTERFACE SECP256K1_STATICLIB)
endif()
add_executable(ecdsa_example ecdsa.c)