Bug 152625 – WebKit fails to build with musl libc library

• Component: Platform
• Status: RESOLVED FIXED

[Khem Raj]

when building webkit2 with musl C library we end up with compile errors due to assumptions that C library for Linux is always glibc and it works with uclibc since uclibc pretends to be glibc in so many cases. However this breaks when we use musl C library for system C library on Linux.

Errors like

/home/ubuntu/work/oe/openembedded-core/build/tmp-musl/sysroots/qemuarm/usr/include/c++/5.3.0/arm-oe-linux-musleabi/bits/ctype_inline.h:68:29: error: 'isspace_WTF_Please_use_ASCIICType_instead_of_ctype_see_comment_in_ASCIICType_h' was not declared in this scope
       __testis = isspace(__c);

show up

[Khem Raj]

Created attachment 268056 [details]
Patch to fix build errors on musl

Proposed fix.

[Alexey Proskuryakov]

Comment on attachment 268056 [details]
Patch to fix build errors on musl

View in context: https://bugs.webkit.org/attachment.cgi?id=268056&action=review

> Source/WebCore/platform/linux/MemoryPressureHandlerLinux.cpp:204
>      ReliefLogger log("Run malloc_trim");

Shouldn't this be inside the ifdef? Otherwise, it's not telling the truth.

[Khem Raj]

Created attachment 268060 [details]
updated patch

Addresses review comments and additionally also makes sure that backtrace)() API is limited to glibc/uclibc only.

[Daniel Bates]

Thank you Khem Raj for the patch. Although the change looks reasonable it cannot be landed because it is missing a ChangeLog entry. Please use either script prepare-ChangeLog or webkit-patch to generate a template ChangeLog entry. See <https://webkit.org/contributing-code/#changelogs> for more details, including an example of a well-written ChangeLog entry.

[Khem Raj]

Created attachment 268112 [details]
patch v3

This adds ChangeLog entries as suggested by Daniel

[WebKit Commit Bot]

Attachment 268112 [details] did not pass style-queue:


ERROR: Source/WTF/ChangeLog:8:  Need whitespace between colon and description  [changelog/filechangedescriptionwhitespace] [5]
ERROR: Source/WTF/ChangeLog:13:  Need whitespace between colon and description  [changelog/filechangedescriptionwhitespace] [5]
Total errors found: 2 in 7 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Daniel Bates]

Comment on attachment 268112 [details]
patch v3

View in context: https://bugs.webkit.org/attachment.cgi?id=268112&action=review

> Source/JavaScriptCore/ChangeLog:4
> +        https://bugs.webkit.org/show_bug.cgi?id=152625
> +        qualify isnan() calls with std namespace.

This ChangeLog entry does not conform to the format described in <https://webkit.org/contributing-code/#changelogs>. In particular, these two lines should be the bug title and bug URL in that order. The description (line 4) should be placed under the Reviewed by line and begin with a capital letter (Q). We should also explain in the description that the motivation of this change is to fix the build when building with the musl libc library on Linux. I also suggest that we omit the description of Option::operator== (line 9) because this ChangeLog only describes a change to a single function, Option::operator==, and the change description for Option::operator== (line 9) is almost the same as the description (line 4). Making the above changes, we have: 

2016-01-02 Khem Raj <[e-mail]>
        
        WebKit fails to build with musl libc library
        https://bugs.webkit.org/show_bug.cgi?id=152625

        Reviewed by Daniel Bates.

        Qualify isnan() calls with std namespace to fix the build when building with the musl libc library on Linux.

        * runtime/Options.cpp:
        (Option::operator==):

> Source/WTF/ChangeLog:4
> +        Disable ctype.h check for musl C library on Linux.

Similar to my remarks for the ChangeLog entry in Source/JavaScriptCore/ChangeLog, please move this description under the Reviewed by line, change line 3 to the the bug title ("WebKit fails to build with musl libc library") and change line 4 to be bug URL (https://bugs.webkit.org/show_bug.cgi?id=152625).

> Source/WTF/ChangeLog:8
> +        * wtf/DisallowCType.h

Please add a colon character (:) at the end of this line to fix the style bot warning (*):

ERROR: Source/WTF/ChangeLog:8:  Need whitespace between colon and description  [changelog/filechangedescriptionwhitespace] [5]

(*) This error message is disingenuous. The actual error is that there is no colon character after the filename. We should teach the style bot to detect the omission of the ':' and provide a better error message. This work should be done in a separate bug.

> Source/WTF/ChangeLog:10
> +        Enable backtrace on linux when using glibc

linux => Linux

Please add a period to the end of this sentence.

(These are very small issues. As part of addressing the bug title/description corrections I suggest we also make these changes).

> Source/WTF/ChangeLog:11
> +        We dont have backtrace() implemented on non-glibc libc's on Linux.

dont => don't

(This is a very small issue. As part of addressing the bug title/description corrections I suggest we also make this change).

> Source/WTF/ChangeLog:13
> +        * wtf/Assertions.cpp

Please add a colon character (:) at the end of this line to fix the style bot warning (*):

ERROR: Source/WTF/ChangeLog:13:  Need whitespace between colon and description  [changelog/filechangedescriptionwhitespace] [5]

> Source/WTF/wtf/Assertions.cpp:71
> +#if OS(DARWIN) || (OS(LINUX) && defined(__GLIBC__) && !defined(__UCLIBC__))

For completeness, we must explicitly check for !defined(__UCLIBC__) (i.e. cannot check OS(LINUX) && defined(__GLIBC__)) because uClibc usually defines __GLIBC__ when being compiled per <https://git.uclibc.org/uClibc/tree/include/features.h?id=266bdc1f623fe6fe489e5115e0f8ef723705d949>. The criterion for defining __GLIBC__ and the motivation for doing so is described at <https://git.uclibc.org/uClibc/tree/include/features.h?id=266bdc1f623fe6fe489e5115e0f8ef723705d949#n81> and <https://git.uclibc.org/uClibc/tree/include/features.h?id=266bdc1f623fe6fe489e5115e0f8ef723705d949#n376>.

On another note, the musl libc project does not expose any preprocessor macros to identify the use of the musl libc library during compilation as a matter of policy (http://wiki.musl-libc.org/wiki/FAQ#Q:_why_is_there_no_MUSL_macro_.3F).

[Daniel Bates]

Comment on attachment 268112 [details]
patch v3

View in context: https://bugs.webkit.org/attachment.cgi?id=268112&action=review

> Source/WebCore/ChangeLog:4
> +        https://bugs.webkit.org/show_bug.cgi?id=152625
> +        malloc_trim is glibc specific API so guard it with __GLIBC__.

Similar to my remarks for the ChangeLog entry in Source/JavaScriptCore/ChangeLog and Source/WTF/ChangeLog, please move this description under the Reviewed by line, change line 3 to the the bug title ("WebKit fails to build with musl libc library") and change line 4 to be bug URL (https://bugs.webkit.org/show_bug.cgi?id=152625).

[Khem Raj]

(In reply to comment #7)
> Comment on attachment 268112 [details]
> patch v3
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=268112&action=review
> 
> > Source/JavaScriptCore/ChangeLog:4
> > +        https://bugs.webkit.org/show_bug.cgi?id=152625
> > +        qualify isnan() calls with std namespace.
> 
> This ChangeLog entry does not conform to the format described in
> <https://webkit.org/contributing-code/#changelogs>. In particular, these two
> lines should be the bug title and bug URL in that order. The description
> (line 4) should be placed under the Reviewed by line and begin with a
> capital letter (Q). We should also explain in the description that the
> motivation of this change is to fix the build when building with the musl
> libc library on Linux. I also suggest that we omit the description of
> Option::operator== (line 9) because this ChangeLog only describes a change
> to a single function, Option::operator==, and the change description for
> Option::operator== (line 9) is almost the same as the description (line 4).
> Making the above changes, we have: 
> 
> 2016-01-02 Khem Raj <[e-mail]>
>         
>         WebKit fails to build with musl libc library
>         https://bugs.webkit.org/show_bug.cgi?id=152625
> 
>         Reviewed by Daniel Bates.
> 
>         Qualify isnan() calls with std namespace to fix the build when
> building with the musl libc library on Linux.
> 
>         * runtime/Options.cpp:
>         (Option::operator==):
> 
> > Source/WTF/ChangeLog:4
> > +        Disable ctype.h check for musl C library on Linux.
> 
> Similar to my remarks for the ChangeLog entry in
> Source/JavaScriptCore/ChangeLog, please move this description under the
> Reviewed by line, change line 3 to the the bug title ("WebKit fails to build
> with musl libc library") and change line 4 to be bug URL
> (https://bugs.webkit.org/show_bug.cgi?id=152625).
> 
> > Source/WTF/ChangeLog:8
> > +        * wtf/DisallowCType.h
> 
> Please add a colon character (:) at the end of this line to fix the style
> bot warning (*):
> 
> ERROR: Source/WTF/ChangeLog:8:  Need whitespace between colon and
> description  [changelog/filechangedescriptionwhitespace] [5]
> 
> (*) This error message is disingenuous. The actual error is that there is no
> colon character after the filename. We should teach the style bot to detect
> the omission of the ':' and provide a better error message. This work should
> be done in a separate bug.
> 
> > Source/WTF/ChangeLog:10
> > +        Enable backtrace on linux when using glibc
> 
> linux => Linux
> 
> Please add a period to the end of this sentence.
> 
> (These are very small issues. As part of addressing the bug
> title/description corrections I suggest we also make these changes).
> 
> > Source/WTF/ChangeLog:11
> > +        We dont have backtrace() implemented on non-glibc libc's on Linux.
> 
> dont => don't
> 
> (This is a very small issue. As part of addressing the bug title/description
> corrections I suggest we also make this change).
> 
> > Source/WTF/ChangeLog:13
> > +        * wtf/Assertions.cpp
> 
> Please add a colon character (:) at the end of this line to fix the style
> bot warning (*):
> 
> ERROR: Source/WTF/ChangeLog:13:  Need whitespace between colon and
> description  [changelog/filechangedescriptionwhitespace] [5]
> 
> > Source/WTF/wtf/Assertions.cpp:71
> > +#if OS(DARWIN) || (OS(LINUX) && defined(__GLIBC__) && !defined(__UCLIBC__))
> 
> For completeness, we must explicitly check for !defined(__UCLIBC__) (i.e.
> cannot check OS(LINUX) && defined(__GLIBC__)) because uClibc usually defines
> __GLIBC__ when being compiled per
> <https://git.uclibc.org/uClibc/tree/include/features.
> h?id=266bdc1f623fe6fe489e5115e0f8ef723705d949>. The criterion for defining
> __GLIBC__ and the motivation for doing so is described at
> <https://git.uclibc.org/uClibc/tree/include/features.
> h?id=266bdc1f623fe6fe489e5115e0f8ef723705d949#n81> and
> <https://git.uclibc.org/uClibc/tree/include/features.
> h?id=266bdc1f623fe6fe489e5115e0f8ef723705d949#n376>.
> 
> On another note, the musl libc project does not expose any preprocessor
> macros to identify the use of the musl libc library during compilation as a
> matter of policy
> (http://wiki.musl-libc.org/wiki/FAQ#Q:_why_is_there_no_MUSL_macro_.3F).

backtrace() is not implemented on uclibc as well. So this fix also fixes uclibc builds

[Khem Raj]

Created attachment 268143 [details]
patch v4

[WebKit Commit Bot]

Comment on attachment 268143 [details]
patch v4

Clearing flags on attachment: 268143

Committed r194518: <http://trac.webkit.org/changeset/194518>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.