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http: optionally load libcurl lazily
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This compile-time option allows to ask Git to load libcurl dynamically
at runtime.

Together with a follow-up patch that optionally overrides the file name
depending on the `http.sslBackend` setting, this kicks open the door for
installing multiple libcurl flavors side by side, and load the one
corresponding to the (runtime-)configured SSL/TLS backend.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
@dscho
dscho committed Feb 14, 2024
1 parent 1977b0d commit 456b684
Showing 2 changed files with 365 additions and 7 deletions.
28 changes: 21 additions & 7 deletions Makefile
View file
Original file line number Diff line number Diff line change
@@ -464,6 +464,11 @@ include shared.mak
#
# CURL_LDFLAGS=-lcurl
#
# Define LAZYLOAD_LIBCURL to dynamically load the libcurl; This can be useful
# if Multiple libcurl versions exist (with different file names) that link to
# various SSL/TLS backends, to support the `http.sslBackend` runtime switch in
# such a scenario.
#
# === Optional library: libpcre2 ===
#
# Define USE_LIBPCRE if you have and want to use libpcre. Various
@@ -1616,10 +1621,19 @@ else
CURL_LIBCURL =
endif

ifndef CURL_LDFLAGS
CURL_LDFLAGS = $(eval CURL_LDFLAGS := $$(shell $$(CURL_CONFIG) --libs))$(CURL_LDFLAGS)
ifdef LAZYLOAD_LIBCURL
LAZYLOAD_LIBCURL_OBJ = compat/lazyload-curl.o
OBJECTS += $(LAZYLOAD_LIBCURL_OBJ)
# The `CURL_STATICLIB` constant must be defined to avoid seeing the functions
# declared as DLL imports
CURL_CFLAGS = -DCURL_STATICLIB
CURL_LIBCURL = -ldl
else
ifndef CURL_LDFLAGS
CURL_LDFLAGS = $(eval CURL_LDFLAGS := $$(shell $$(CURL_CONFIG) --libs))$(CURL_LDFLAGS)
endif
CURL_LIBCURL += $(CURL_LDFLAGS)
endif
CURL_LIBCURL += $(CURL_LDFLAGS)

ifndef CURL_CFLAGS
CURL_CFLAGS = $(eval CURL_CFLAGS := $$(shell $$(CURL_CONFIG) --cflags))$(CURL_CFLAGS)
@@ -1640,7 +1654,7 @@ else
endif
ifdef USE_CURL_FOR_IMAP_SEND
BASIC_CFLAGS += -DUSE_CURL_FOR_IMAP_SEND
IMAP_SEND_BUILDDEPS = http.o
IMAP_SEND_BUILDDEPS = http.o $(LAZYLOAD_LIBCURL_OBJ)
IMAP_SEND_LDFLAGS += $(CURL_LIBCURL)
endif
ifndef NO_EXPAT
@@ -2812,10 +2826,10 @@ git-imap-send$X: imap-send.o $(IMAP_SEND_BUILDDEPS) GIT-LDFLAGS $(GITLIBS)
$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
$(IMAP_SEND_LDFLAGS) $(LIBS)

git-http-fetch$X: http.o http-walker.o http-fetch.o GIT-LDFLAGS $(GITLIBS)
git-http-fetch$X: http.o http-walker.o http-fetch.o $(LAZYLOAD_LIBCURL_OBJ) GIT-LDFLAGS $(GITLIBS)
$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
$(CURL_LIBCURL) $(LIBS)
git-http-push$X: http.o http-push.o GIT-LDFLAGS $(GITLIBS)
git-http-push$X: http.o http-push.o $(LAZYLOAD_LIBCURL_OBJ) GIT-LDFLAGS $(GITLIBS)
$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
$(CURL_LIBCURL) $(EXPAT_LIBEXPAT) $(LIBS)

@@ -2825,7 +2839,7 @@ $(REMOTE_CURL_ALIASES): $(REMOTE_CURL_PRIMARY)
ln -s $< $@ 2>/dev/null || \
cp $< $@

$(REMOTE_CURL_PRIMARY): remote-curl.o http.o http-walker.o GIT-LDFLAGS $(GITLIBS)
$(REMOTE_CURL_PRIMARY): remote-curl.o http.o http-walker.o $(LAZYLOAD_LIBCURL_OBJ) GIT-LDFLAGS $(GITLIBS)
$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
$(CURL_LIBCURL) $(EXPAT_LIBEXPAT) $(LIBS)

344 changes: 344 additions & 0 deletions compat/lazyload-curl.c
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,344 @@
#include "../git-compat-util.h"
#include "../git-curl-compat.h"
#include <dlfcn.h>

/*
* The ABI version of libcurl is encoded in its shared libraries' file names.
* This ABI version has not changed since October 2006 and is unlikely to be
* changed in the future. See https://curl.se/libcurl/abi.html for details.
*/
#define LIBCURL_ABI_VERSION "4"

typedef void (*func_t)(void);

#ifdef __APPLE__
#define LIBCURL_FILE_NAME(base) base "." LIBCURL_ABI_VERSION ".dylib"
#else
#define LIBCURL_FILE_NAME(base) base ".so." LIBCURL_ABI_VERSION
#endif

static void *load_library(const char *name)
{
return dlopen(name, RTLD_LAZY);
}

static func_t load_function(void *handle, const char *name)
{
/*
* Casting the return value of `dlsym()` to a function pointer is
* explicitly allowed in recent POSIX standards, but GCC complains
* about this in pedantic mode nevertheless. For more about this issue,
* see https://stackoverflow.com/q/31526876/1860823 and
* http://stackoverflow.com/a/36385690/1905491.
*/
func_t f;
*(void **)&f = dlsym(handle, name);
return f;
}

typedef char *(*curl_easy_escape_type)(CURL *handle, const char *string, int length);
static curl_easy_escape_type curl_easy_escape_func;

typedef void (*curl_free_type)(void *p);
static curl_free_type curl_free_func;

typedef CURLcode (*curl_global_init_type)(long flags);
static curl_global_init_type curl_global_init_func;

typedef CURLsslset (*curl_global_sslset_type)(curl_sslbackend id, const char *name, const curl_ssl_backend ***avail);
static curl_global_sslset_type curl_global_sslset_func;

typedef void (*curl_global_cleanup_type)(void);
static curl_global_cleanup_type curl_global_cleanup_func;

typedef struct curl_slist *(*curl_slist_append_type)(struct curl_slist *list, const char *data);
static curl_slist_append_type curl_slist_append_func;

typedef void (*curl_slist_free_all_type)(struct curl_slist *list);
static curl_slist_free_all_type curl_slist_free_all_func;

typedef const char *(*curl_easy_strerror_type)(CURLcode error);
static curl_easy_strerror_type curl_easy_strerror_func;

typedef CURLM *(*curl_multi_init_type)(void);
static curl_multi_init_type curl_multi_init_func;

typedef CURLMcode (*curl_multi_add_handle_type)(CURLM *multi_handle, CURL *curl_handle);
static curl_multi_add_handle_type curl_multi_add_handle_func;

typedef CURLMcode (*curl_multi_remove_handle_type)(CURLM *multi_handle, CURL *curl_handle);
static curl_multi_remove_handle_type curl_multi_remove_handle_func;

typedef CURLMcode (*curl_multi_fdset_type)(CURLM *multi_handle, fd_set *read_fd_set, fd_set *write_fd_set, fd_set *exc_fd_set, int *max_fd);
static curl_multi_fdset_type curl_multi_fdset_func;

typedef CURLMcode (*curl_multi_perform_type)(CURLM *multi_handle, int *running_handles);
static curl_multi_perform_type curl_multi_perform_func;

typedef CURLMcode (*curl_multi_cleanup_type)(CURLM *multi_handle);
static curl_multi_cleanup_type curl_multi_cleanup_func;

typedef CURLMsg *(*curl_multi_info_read_type)(CURLM *multi_handle, int *msgs_in_queue);
static curl_multi_info_read_type curl_multi_info_read_func;

typedef const char *(*curl_multi_strerror_type)(CURLMcode error);
static curl_multi_strerror_type curl_multi_strerror_func;

typedef CURLMcode (*curl_multi_timeout_type)(CURLM *multi_handle, long *milliseconds);
static curl_multi_timeout_type curl_multi_timeout_func;

typedef CURL *(*curl_easy_init_type)(void);
static curl_easy_init_type curl_easy_init_func;

typedef CURLcode (*curl_easy_perform_type)(CURL *curl);
static curl_easy_perform_type curl_easy_perform_func;

typedef void (*curl_easy_cleanup_type)(CURL *curl);
static curl_easy_cleanup_type curl_easy_cleanup_func;

typedef CURL *(*curl_easy_duphandle_type)(CURL *curl);
static curl_easy_duphandle_type curl_easy_duphandle_func;

typedef CURLcode (*curl_easy_getinfo_long_type)(CURL *curl, CURLINFO info, long *value);
static curl_easy_getinfo_long_type curl_easy_getinfo_long_func;

typedef CURLcode (*curl_easy_getinfo_pointer_type)(CURL *curl, CURLINFO info, void **value);
static curl_easy_getinfo_pointer_type curl_easy_getinfo_pointer_func;

typedef CURLcode (*curl_easy_getinfo_off_t_type)(CURL *curl, CURLINFO info, curl_off_t *value);
static curl_easy_getinfo_off_t_type curl_easy_getinfo_off_t_func;

typedef CURLcode (*curl_easy_setopt_long_type)(CURL *curl, CURLoption opt, long value);
static curl_easy_setopt_long_type curl_easy_setopt_long_func;

typedef CURLcode (*curl_easy_setopt_pointer_type)(CURL *curl, CURLoption opt, void *value);
static curl_easy_setopt_pointer_type curl_easy_setopt_pointer_func;

typedef CURLcode (*curl_easy_setopt_off_t_type)(CURL *curl, CURLoption opt, curl_off_t value);
static curl_easy_setopt_off_t_type curl_easy_setopt_off_t_func;

static void lazy_load_curl(void)
{
static int initialized;
void *libcurl;
func_t curl_easy_getinfo_func, curl_easy_setopt_func;

if (initialized)
return;

initialized = 1;
libcurl = load_library(LIBCURL_FILE_NAME("libcurl"));
if (!libcurl)
die("failed to load library '%s'", LIBCURL_FILE_NAME("libcurl"));

curl_easy_escape_func = (curl_easy_escape_type)load_function(libcurl, "curl_easy_escape");
curl_free_func = (curl_free_type)load_function(libcurl, "curl_free");
curl_global_init_func = (curl_global_init_type)load_function(libcurl, "curl_global_init");
curl_global_sslset_func = (curl_global_sslset_type)load_function(libcurl, "curl_global_sslset");
curl_global_cleanup_func = (curl_global_cleanup_type)load_function(libcurl, "curl_global_cleanup");
curl_slist_append_func = (curl_slist_append_type)load_function(libcurl, "curl_slist_append");
curl_slist_free_all_func = (curl_slist_free_all_type)load_function(libcurl, "curl_slist_free_all");
curl_easy_strerror_func = (curl_easy_strerror_type)load_function(libcurl, "curl_easy_strerror");
curl_multi_init_func = (curl_multi_init_type)load_function(libcurl, "curl_multi_init");
curl_multi_add_handle_func = (curl_multi_add_handle_type)load_function(libcurl, "curl_multi_add_handle");
curl_multi_remove_handle_func = (curl_multi_remove_handle_type)load_function(libcurl, "curl_multi_remove_handle");
curl_multi_fdset_func = (curl_multi_fdset_type)load_function(libcurl, "curl_multi_fdset");
curl_multi_perform_func = (curl_multi_perform_type)load_function(libcurl, "curl_multi_perform");
curl_multi_cleanup_func = (curl_multi_cleanup_type)load_function(libcurl, "curl_multi_cleanup");
curl_multi_info_read_func = (curl_multi_info_read_type)load_function(libcurl, "curl_multi_info_read");
curl_multi_strerror_func = (curl_multi_strerror_type)load_function(libcurl, "curl_multi_strerror");
curl_multi_timeout_func = (curl_multi_timeout_type)load_function(libcurl, "curl_multi_timeout");
curl_easy_init_func = (curl_easy_init_type)load_function(libcurl, "curl_easy_init");
curl_easy_perform_func = (curl_easy_perform_type)load_function(libcurl, "curl_easy_perform");
curl_easy_cleanup_func = (curl_easy_cleanup_type)load_function(libcurl, "curl_easy_cleanup");
curl_easy_duphandle_func = (curl_easy_duphandle_type)load_function(libcurl, "curl_easy_duphandle");

curl_easy_getinfo_func = load_function(libcurl, "curl_easy_getinfo");
curl_easy_getinfo_long_func = (curl_easy_getinfo_long_type)curl_easy_getinfo_func;
curl_easy_getinfo_pointer_func = (curl_easy_getinfo_pointer_type)curl_easy_getinfo_func;
curl_easy_getinfo_off_t_func = (curl_easy_getinfo_off_t_type)curl_easy_getinfo_func;

curl_easy_setopt_func = load_function(libcurl, "curl_easy_setopt");
curl_easy_setopt_long_func = (curl_easy_setopt_long_type)curl_easy_setopt_func;
curl_easy_setopt_pointer_func = (curl_easy_setopt_pointer_type)curl_easy_setopt_func;
curl_easy_setopt_off_t_func = (curl_easy_setopt_off_t_type)curl_easy_setopt_func;
}

char *curl_easy_escape(CURL *handle, const char *string, int length)
{
lazy_load_curl();
return curl_easy_escape_func(handle, string, length);
}

void curl_free(void *p)
{
lazy_load_curl();
curl_free_func(p);
}

CURLcode curl_global_init(long flags)
{
lazy_load_curl();
return curl_global_init_func(flags);
}

CURLsslset curl_global_sslset(curl_sslbackend id, const char *name, const curl_ssl_backend ***avail)
{
lazy_load_curl();
return curl_global_sslset_func(id, name, avail);
}

void curl_global_cleanup(void)
{
lazy_load_curl();
curl_global_cleanup_func();
}

struct curl_slist *curl_slist_append(struct curl_slist *list, const char *data)
{
lazy_load_curl();
return curl_slist_append_func(list, data);
}

void curl_slist_free_all(struct curl_slist *list)
{
lazy_load_curl();
curl_slist_free_all_func(list);
}

const char *curl_easy_strerror(CURLcode error)
{
lazy_load_curl();
return curl_easy_strerror_func(error);
}

CURLM *curl_multi_init(void)
{
lazy_load_curl();
return curl_multi_init_func();
}

CURLMcode curl_multi_add_handle(CURLM *multi_handle, CURL *curl_handle)
{
lazy_load_curl();
return curl_multi_add_handle_func(multi_handle, curl_handle);
}

CURLMcode curl_multi_remove_handle(CURLM *multi_handle, CURL *curl_handle)
{
lazy_load_curl();
return curl_multi_remove_handle_func(multi_handle, curl_handle);
}

CURLMcode curl_multi_fdset(CURLM *multi_handle, fd_set *read_fd_set, fd_set *write_fd_set, fd_set *exc_fd_set, int *max_fd)
{
lazy_load_curl();
return curl_multi_fdset_func(multi_handle, read_fd_set, write_fd_set, exc_fd_set, max_fd);
}

CURLMcode curl_multi_perform(CURLM *multi_handle, int *running_handles)
{
lazy_load_curl();
return curl_multi_perform_func(multi_handle, running_handles);
}

CURLMcode curl_multi_cleanup(CURLM *multi_handle)
{
lazy_load_curl();
return curl_multi_cleanup_func(multi_handle);
}

CURLMsg *curl_multi_info_read(CURLM *multi_handle, int *msgs_in_queue)
{
lazy_load_curl();
return curl_multi_info_read_func(multi_handle, msgs_in_queue);
}

const char *curl_multi_strerror(CURLMcode error)
{
lazy_load_curl();
return curl_multi_strerror_func(error);
}

CURLMcode curl_multi_timeout(CURLM *multi_handle, long *milliseconds)
{
lazy_load_curl();
return curl_multi_timeout_func(multi_handle, milliseconds);
}

CURL *curl_easy_init(void)
{
lazy_load_curl();
return curl_easy_init_func();
}

CURLcode curl_easy_perform(CURL *curl)
{
lazy_load_curl();
return curl_easy_perform_func(curl);
}

void curl_easy_cleanup(CURL *curl)
{
lazy_load_curl();
curl_easy_cleanup_func(curl);
}

CURL *curl_easy_duphandle(CURL *curl)
{
lazy_load_curl();
return curl_easy_duphandle_func(curl);
}

#ifndef CURL_IGNORE_DEPRECATION
#define CURL_IGNORE_DEPRECATION(x) x
#endif

#ifndef CURLOPTTYPE_BLOB
#define CURLOPTTYPE_BLOB 40000
#endif

#undef curl_easy_getinfo
CURLcode curl_easy_getinfo(CURL *curl, CURLINFO info, ...)
{
va_list ap;
CURLcode res;

va_start(ap, info);
lazy_load_curl();
CURL_IGNORE_DEPRECATION(
if (info >= CURLINFO_LONG && info < CURLINFO_DOUBLE)
res = curl_easy_getinfo_long_func(curl, info, va_arg(ap, long *));
else if ((info >= CURLINFO_STRING && info < CURLINFO_LONG) ||
(info >= CURLINFO_SLIST && info < CURLINFO_SOCKET))
res = curl_easy_getinfo_pointer_func(curl, info, va_arg(ap, void **));
else if (info >= CURLINFO_OFF_T)
res = curl_easy_getinfo_off_t_func(curl, info, va_arg(ap, curl_off_t *));
else
die("%s:%d: TODO (info: %d)!", __FILE__, __LINE__, info);
)
va_end(ap);
return res;
}

#undef curl_easy_setopt
CURLcode curl_easy_setopt(CURL *curl, CURLoption opt, ...)
{
va_list ap;
CURLcode res;

va_start(ap, opt);
lazy_load_curl();
CURL_IGNORE_DEPRECATION(
if (opt >= CURLOPTTYPE_LONG && opt < CURLOPTTYPE_OBJECTPOINT)
res = curl_easy_setopt_long_func(curl, opt, va_arg(ap, long));
else if (opt >= CURLOPTTYPE_OBJECTPOINT && opt < CURLOPTTYPE_OFF_T)
res = curl_easy_setopt_pointer_func(curl, opt, va_arg(ap, void *));
else if (opt >= CURLOPTTYPE_OFF_T && opt < CURLOPTTYPE_BLOB)
res = curl_easy_setopt_off_t_func(curl, opt, va_arg(ap, curl_off_t));
else
die("%s:%d: TODO (opt: %d)!", __FILE__, __LINE__, opt);
)
va_end(ap);
return res;
}

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