Improve the linking of libraries #1338

akosthekiss · 2016-09-11T01:05:08Z

Although both jerry-libc and jerry-libm have configuration options
that enable/disable their build, in practice, only jerry-libc can be
replaced with the system (compiler-default) libc. If jerry-libm is
disabled, the build of jerry-main fails, as there is no way to
instruct the linker to link the system libm to the binary. (The
build system does have a way to pass flags to the linker, but those
flags are listed before the linked objects. For the references to
get resolved correctly, the libraries to be linked have to be
specified after the objects.)

This patch adds the EXTERNAL_LINK_LIBS configuration option to
CMakeLists, which ensures that the specified libraries get
correctly passed to the linker. (E.g, replacing jerry-libm with
system libm becomes possible with
JERRY_LIBM=OFF EXTERNAL_LINK_LIBS='-lm'.)

Additionally, the patch also makes the following related changes:

Removes the COMPILER_DEFAULT_LIBC configuration option, as it is
(almost) always the opposite of JERRY_LIBC. Moreover, its name is
misleading: its only role is to add -nostdlib to the linker
flags.
Makes use of transitive library dependencies: if a library has
another library as dependency, and it is linked to a binary, its
dependency is linked as well. Thus, jerry-libc, jerry-libm, and
any external libraries are added to jerry-core as dependency, and
then only jerry-core is linked to executables (cmake will take
care of the rest).
build.py and run-tests.py follow up the changes, along with some
minor syntax changes.
Moves static linking option to global CMakeLists, as unit test
binaries should be linked the same way as jerry-main.
Adds EXTERNAL_COMPILER_FLAGS and EXTERNAL_LINKER_FLAGS as last to
the flag list, to allow user override of (nearly) anything.

The patch speculatively follows up the build system changes in the
mbed, riot-stm32f4, and zephyr targets.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss [email protected]

akosthekiss · 2016-09-11T01:06:42Z

Example use cases:

Default, e.g., statically linked Linux binaries:
JERRY_LIBC=ON JERRY_LIBM=ON ENABLE_STATIC_LINK=ON

Linux or Tizen binaries dynamically linked to system libs:
JERRY_LIBC=OFF JERRY_LIBM=OFF EXTERNAL_LINK_LIBS='-lm' ENABLE_STATIC_LINK=OFF

OS X binaries:
JERRY_LIBC=OFF JERRY_LIBM=OFF ENABLE_STATIC_LINK=OFF
('-lSystem' is automatically added by the build system)

Experiment results on x86-64/Linux:

tools/build.py: (default opts)
- ldd: not a dynamic executable
- size: 233573 text, 16 data, 2626072 bss
tools/build.py: --jerry-libc=off
- ldd: not a dynamic executable
- size: 1012949 text, 7764 data, 2635776 bss
tools/build.py: --jerry-libc=off --jerry-libm=off --link-lib='-lm'
- ldd: not a dynamic executable
- size: 1843941 text, 7900 data, 2635776 bss
tools/build.py: --static-link=off
- ldd: not a dynamic executable
- size: 236517 text, 16 data, 2626072 bss
tools/build.py: --jerry-libc=off --static-link=off
- ldd: linux-vdso.so.1, libc.so.6, /lib64/ld-linux-x86-64.so.2
- size: 232376 text, 704 data, 2626136 bss
tools/build.py: --jerry-libc=off --jerry-libm=off --link-lib='-lm' --static-link=off
- ldd: linux-vdso.so.1, libc.so.6, libm.so.6, /lib64/ld-linux-x86-64.so.2
- size: 219850 text, 848 data, 2626136 bss

robertsipka · 2016-09-11T14:21:41Z

I like this patch, especially that you removed the the COMPILER_DEFAULT_LIBC option, it was quite confusing. Could you please also update the GETTING-STARTED documentation?

LaszloLango · 2016-09-12T06:24:35Z

jerry-core/CMakeLists.txt

@@ -201,13 +201,19 @@ add_library(${JERRY_CORE_NAME} STATIC ${SOURCE_CORE})
 target_compile_definitions(${JERRY_CORE_NAME} PUBLIC ${DEFINES_JERRY})
 target_include_directories(${JERRY_CORE_NAME} PUBLIC ${INCLUDE_CORE})

-if (JERRY_LIBC)
+set(JERRY_LIBS )


Is the space before the left parenthesis intentional?

Yes, JERRY_LIBS is set to empty string. Without that space it just looked like a predicate ("if(JERRY_LIBS)") to me.

LaszloLango · 2016-09-12T06:29:53Z

LGTM

akosthekiss · 2016-09-12T06:33:16Z

@sergioamr Could you please take a look at the zephyr-related part? I did my best guess not to break the build there but could not try it in practice.

sergioamr · 2016-09-12T07:10:21Z

@poussa Sakari, i will be in the thingmonk conference this week so i will probably don't have access to build this. Could you have a look? Thanks

Although both jerry-libc and jerry-libm have configuration options that enable/disable their build, in practice, only jerry-libc can be replaced with the system (compiler-default) libc. If jerry-libm is disabled, the build of jerry-main fails, as there is no way to instruct the linker to link the system libm to the binary. (The build system does have a way to pass flags to the linker, but those flags are listed before the linked objects. For the references to get resolved correctly, the libraries to be linked have to be specified _after_ the objects.) This patch adds the EXTERNAL_LINK_LIBS configuration option to CMakeLists, which ensures that the specified libraries get correctly passed to the linker. (E.g, replacing jerry-libm with system libm becomes possible with `JERRY_LIBM=OFF EXTERNAL_LINK_LIBS='-lm'`.) Additionally, the patch also makes the following related changes: * Removes the COMPILER_DEFAULT_LIBC configuration option, as it is (almost) always the opposite of JERRY_LIBC. Moreover, its name is misleading: its only role is to add `-nostdlib` to the linker flags. * Makes use of transitive library dependencies: if a library has another library as dependency, and it is linked to a binary, its dependency is linked as well. Thus, jerry-libc, jerry-libm, and any external libraries are added to jerry-core as dependency, and then only jerry-core is linked to executables (cmake will take care of the rest). * build.py and run-tests.py follow up the changes, along with some minor syntax changes. * Moves static linking option to global CMakeLists, as unit test binaries should be linked the same way as jerry-main. * Adds EXTERNAL_COMPILER_FLAGS and EXTERNAL_LINKER_FLAGS as last to the flag list, to allow user override of (nearly) anything. The patch speculatively follows up the build system changes in the mbed, riot-stm32f4, and zephyr targets. JerryScript-DCO-1.0-Signed-off-by: Akos Kiss [email protected]

akosthekiss · 2016-09-12T12:10:10Z

@robertsipka Thanks for reminding me of the docs. Updated.

dbatyai · 2016-09-14T13:08:25Z

LGTM

akosthekiss · 2016-09-14T13:19:22Z

@sergioamr @poussa Any feedback that would block landing this?

sergioamr · 2016-09-14T13:44:24Z

@akosthekiss Sorry, still at Thinkmonk conference. Tomorrow i will be back in the office.

poussa · 2016-09-14T16:19:30Z

Sorry here as well - did not had time for this recently.

sergioamr · 2016-09-15T10:35:40Z

LGTM, sorry about the delay

akosthekiss · 2016-09-15T11:07:21Z

@sergioamr Thanks a lot!

Although both jerry-libc and jerry-libm have configuration options that enable/disable their build, in practice, only jerry-libc can be replaced with the system (compiler-default) libc. If jerry-libm is disabled, the build of jerry-main fails, as there is no way to instruct the linker to link the system libm to the binary. (The build system does have a way to pass flags to the linker, but those flags are listed before the linked objects. For the references to get resolved correctly, the libraries to be linked have to be specified _after_ the objects.) This patch adds the EXTERNAL_LINK_LIBS configuration option to CMakeLists, which ensures that the specified libraries get correctly passed to the linker. (E.g, replacing jerry-libm with system libm becomes possible with `JERRY_LIBM=OFF EXTERNAL_LINK_LIBS='-lm'`.) Additionally, the patch also makes the following related changes: * Removes the COMPILER_DEFAULT_LIBC configuration option, as it is (almost) always the opposite of JERRY_LIBC. Moreover, its name is misleading: its only role is to add `-nostdlib` to the linker flags. * Makes use of transitive library dependencies: if a library has another library as dependency, and it is linked to a binary, its dependency is linked as well. Thus, jerry-libc, jerry-libm, and any external libraries are added to jerry-core as dependency, and then only jerry-core is linked to executables (cmake will take care of the rest). * build.py and run-tests.py follow up the changes, along with some minor syntax changes. * Moves static linking option to global CMakeLists, as unit test binaries should be linked the same way as jerry-main. * Adds EXTERNAL_COMPILER_FLAGS and EXTERNAL_LINKER_FLAGS as last to the flag list, to allow user override of (nearly) anything. The patch speculatively follows up the build system changes in the mbed, riot-stm32f4, and zephyr targets. JerryScript-DCO-1.0-Signed-off-by: Akos Kiss [email protected]

akosthekiss added enhancement An improvement tools Related to the tooling scripts labels Sep 11, 2016

LaszloLango reviewed Sep 12, 2016
View reviewed changes

akosthekiss force-pushed the link-libs branch from d49a2e9 to c424edd Compare September 12, 2016 12:07

akosthekiss merged commit d38ab71 into jerryscript-project:master Sep 15, 2016

akosthekiss deleted the link-libs branch September 15, 2016 11:07

zherczeg mentioned this pull request Mar 27, 2018

Nominating Robert Sipka (robertsipka) to become a reviewer #2254

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Improve the linking of libraries #1338

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