microlib support: Fix build with Arm Compiler 6 and MicroLib #10704

hugueskamba · 2019-05-29T13:44:08Z

Description

Building binaries with MicroLib and Arm compiler 6 has been failing
because of a bug in Arm compiler 6. The compiler introduces a
symbol, __scanf_mbtowc, which is not present in MicroLib C library.

The present commit adds a weak reference to the symbol to allow a
successful linkage. This is a temporary fix until the bug in the
compiler is fixed. It should be removed after the compiler bug is fixed.

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

Building binaries with MicroLib and Arm compiler 6 has been failing because of a bug in Arm compiler 6. The compiler introduces a symbol, `__scanf_mbtowc`, which is not present in MicroLib C library. The present commit adds a weak reference to the symbol to allow a successful linkage. This is a temporary fix until the bug in the compiler is fixed. It should be removed after the compiler bug is fixed.

ciarmcom · 2019-05-29T15:01:42Z

@hugueskamba, thank you for your changes.
@ARMmbed/mbed-os-core @ARMmbed/mbed-os-maintainers please review.

bulislaw · 2019-05-29T16:49:56Z

rtos/TARGET_CORTEX/TOOLCHAIN_ARM_MICRO/mbed_boot_arm_micro.c

+// for the missing symbol
+#include <stdio.h>
+typedef int ScanfReadRec;
+MBED_WEAK long int _scanf_mbtowc(


Do we know what this function does? Basically what will fail for this setup.

It converts multibyte charaters to wide characters. This function is not used in MicroLib which does not support wide characters or multibyte strings. The compiler inadvertently adds this symbol even if it is not used. There is an internal ticket being looked at by the compiler team which has acknowledged the bug.
The present commit essentially provides a stud for an unused functionality to satisfy the linker.

Can we add here what version is affected (to know when we can remove it) , something along the lines <6.x.x is affected.

Can we add here what version is affected (to know when we can remove it) , something along the lines <6.x.x is affected.

6855093

The info about the compiler versions affected has been last in the last commit.

*lost, correct, I cant find the comment "Arm Compiler 6 version 6.12 and earlier versions are affected." here.

The info about the compiler versions affected has been last in the last commit.

It has now been restored. Thanks.

0xc0170

How was this discovered - any tests failing, or we have missed the coverage?

hugueskamba · 2019-05-31T11:25:22Z

How was this discovered - any tests failing, or we have missed the coverage?

It was discovered by attempting to build an application using the uARM toolchain. We currently do not have a CI test for this. I was planning on adding that next.

0xc0170 · 2019-05-31T12:55:18Z

Started CI meanwhile

mbed-ci · 2019-05-31T17:59:04Z

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts

0xc0170 · 2019-06-04T13:35:30Z

Finalizing reviews, this is ready for integration

adbridge · 2019-06-18T17:06:57Z

@0xc0170 please re-review latest changes

0xc0170

latest forced pushed resulted in missing the requested version

0xc0170 · 2019-06-24T12:42:40Z

rtos/TARGET_CORTEX/TOOLCHAIN_ARM_MICRO/mbed_boot_arm_micro.c

+// for the missing symbol
+#include <stdio.h>
+typedef int ScanfReadRec;
+MBED_WEAK long int _scanf_mbtowc(


*lost, correct, I cant find the comment "Arm Compiler 6 version 6.12 and earlier versions are affected." here.

hugueskamba · 2019-06-24T13:36:33Z

How was this discovered - any tests failing, or we have missed the coverage?

It was discovered by attempting to build an application using the uARM toolchain. We currently do not have a CI test for this. I was planning on adding that next.

Regarding this. A request was made (via Jira) for the test team in Finland to add the test for uARM as they are responsible for adding it.

0xc0170 · 2019-06-24T21:31:17Z

Ci restarted

mbed-ci · 2019-06-25T01:17:36Z

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 2
Build artifacts

0xc0170 · 2019-06-25T10:38:43Z

@hugueskamba if you force push, leave a comment - let everyone know what has changed and why it was updated . This needs now CI again.

0xc0170 · 2019-06-25T10:39:01Z

CI restarted

mbed-ci · 2019-06-25T11:43:58Z

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 3
Build artifacts

0xc0170 · 2019-06-25T12:26:38Z

@evedon All good with this PR?

hugueskamba · 2019-06-25T13:38:16Z

@hugueskamba if you force push, leave a comment - let everyone know what has changed and why it was updated . This needs now CI again.

I am not sure what that force push was as I was not even working on this branch. I need to figure out what is happening. I think when I force push on one branch it somehow push stuff on other branches too. I am investigating this at the moment.

evedon · 2019-06-25T14:13:39Z

All good.

ciarmcom requested review from a team May 29, 2019 15:01

ciarmcom added the needs: review label May 29, 2019

bulislaw reviewed May 29, 2019

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0xc0170 approved these changes May 31, 2019

View reviewed changes

0xc0170 added the release-version: 5.13.1 label Jun 4, 2019

hugueskamba force-pushed the fix-microlib-with-arm-compiler-6 branch from 6855093 to e12889d Compare June 18, 2019 14:43

0xc0170 requested changes Jun 24, 2019

View reviewed changes

0xc0170 added needs: work and removed needs: review labels Jun 24, 2019

hugueskamba force-pushed the fix-microlib-with-arm-compiler-6 branch from e12889d to df16c78 Compare June 24, 2019 13:57

0xc0170 approved these changes Jun 24, 2019

View reviewed changes

0xc0170 added needs: CI and removed needs: work labels Jun 24, 2019

hugueskamba force-pushed the fix-microlib-with-arm-compiler-6 branch from df16c78 to e12889d Compare June 25, 2019 07:59

0xc0170 added needs: review and removed needs: CI labels Jun 25, 2019

0xc0170 added ready for merge and removed needs: review labels Jun 25, 2019

0xc0170 merged commit 7954074 into ARMmbed:master Jun 25, 2019

0xc0170 removed the ready for merge label Jun 25, 2019

0xc0170 mentioned this pull request Jul 3, 2019

microlib builds fail #10878

Closed

hugueskamba deleted the fix-microlib-with-arm-compiler-6 branch July 30, 2019 10:04

RonEld mentioned this pull request Sep 8, 2019

Build failure when building for LPC11U35_401 with ARMC6 ARMmbed/mbed-os-example-blinky-baremetal#15

Closed

microlib support: Fix build with Arm Compiler 6 and MicroLib #10704

microlib support: Fix build with Arm Compiler 6 and MicroLib #10704

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hugueskamba commented May 29, 2019

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