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src: ignore maybe-uninitialized warning string_search#31532

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danbev wants to merge 3 commits intonodejs:masterfrom
danbev:string_search-warnings
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src: ignore maybe-uninitialized warning string_search#31532
danbev wants to merge 3 commits intonodejs:masterfrom
danbev:string_search-warnings

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@danbev danbev commented Jan 27, 2020

Currently, the following compilation warning is generated with GCC
version 8.2.1:

In file included from ../src/node_buffer.cc:29:
../src/string_search.h:
In function ‘size_t node::stringsearch::SearchString(
    node::stringsearch::Vector<const Char>,
    node::stringsearch::Vector<const Char>,
    size_t) [with Char = short unsigned int]’:
../src/string_search.h:113:30: warning:
‘search’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
     return (this->*strategy_)(subject, index);
            ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

../src/string_search.h:
In function ‘size_t node::stringsearch::SearchString(
    node::stringsearch::Vector<const Char>,
    node::stringsearch::Vector<const Char>,
    size_t) [with Char = unsigned char]’:
../src/string_search.h:113:30:
warning: ‘search’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
     return (this->*strategy_)(subject, index);
            ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

The issue here seems to be with the strategy_ field which is a pointer
to a member function, and it is set in the constructor of StringSearch.
It is always set and I've not been able to work around this warning
so this commit suggests adding a pragma for GCC to ignore the warning.

Checklist
  • make -j4 test (UNIX), or vcbuild test (Windows) passes
  • commit message follows commit guidelines

@danbev
src: ignore maybe-uninitialized warning string_search
b520c74 
Currently, the following compilation warning is generated with GCC
version 8.2.1:

In file included from ../src/node_buffer.cc:29:
../src/string_search.h:
In function ‘size_t node::stringsearch::SearchString(
    node::stringsearch::Vector<const Char>,
    node::stringsearch::Vector<const Char>,
    size_t) [with Char = short unsigned int]’:
../src/string_search.h:113:30: warning:
‘search’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
     return (this->*strategy_)(subject, index);
            ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

../src/string_search.h:
In function ‘size_t node::stringsearch::SearchString(
    node::stringsearch::Vector<const Char>,
    node::stringsearch::Vector<const Char>,
    size_t) [with Char = unsigned char]’:
../src/string_search.h:113:30:
warning: ‘search’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
     return (this->*strategy_)(subject, index);
            ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

The issue here seems to be with the `strategy_` field which is a pointer
to a member function, and it is set in the constructor of StringSearch.
It is always set and I've not been able to work around this warning
so this commit suggests adding a pragma for GCC to ignore the warning.
@nodejs-github-bot nodejs-github-bot added buffer Issues and PRs related to the buffer subsystem. c++ Issues and PRs that require attention from people who are familiar with C++. labels Jan 27, 2020
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nodejs-github-bot commented Jan 27, 2020

CI: https://ci.nodejs.org/job/node-test-pull-request/28716/

lundibundi
lundibundi reviewed Jan 29, 2020
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src/string_search.h Outdated
return (this->*strategy_)(subject, index);
#if (__GNUC__ >= 8) && !defined(__clang__)
#pragma GCC diagnostic pop
#endif
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IIUC the issue is not with strategy_, but with the arrays in the StringSearchBase, which are indeed uninitialized (they will be initialized before BoyerMoore search is started)

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@danbev danbev Feb 3, 2020

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@lundibundi Thanks, I'll try to take a closer look at this again this week.

danbev added 2 commits February 3, 2020 09:33
@danbev
Revert "src: ignore maybe-uninitialized warning string_search"
1b3454d 
This reverts commit b520c74.
@danbev
src: ignore maybe-uninitialized warning string_search
b1269ab 
Currently, the following compilation warning is generated with GCC
version 8.2.1:

In file included from ../src/node_buffer.cc:29:
../src/string_search.h:
In function ‘size_t node::stringsearch::SearchString(
    node::stringsearch::Vector<const Char>,
    node::stringsearch::Vector<const Char>,
    size_t) [with Char = short unsigned int]’:
../src/string_search.h:113:30: warning:
‘search’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
     return (this->*strategy_)(subject, index);
            ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

../src/string_search.h:
In function ‘size_t node::stringsearch::SearchString(
    node::stringsearch::Vector<const Char>,
    node::stringsearch::Vector<const Char>,
    size_t) [with Char = unsigned char]’:
../src/string_search.h:113:30:
warning: ‘search’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
     return (this->*strategy_)(subject, index);
            ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

I'm not sure why this works but delegating to the default constructor of
the base class StringSearchBase makes this warning go away.
@lundibundi lundibundi mentioned this pull request Feb 14, 2020
Closed
1 task
bnoordhuis added a commit to bnoordhuis/io.js that referenced this pull request Feb 15, 2020
@bnoordhuis
src: fix -Wmaybe-uninitialized compiler warning
ed8b671 
Turn the `strategy_` method pointer into an enum-based static dispatch.

It's both safer and more secure (no chance of method pointer corruption)
and it helps GCC see that the shift and suffix tables it's complaining
about are unused in single char search mode.

Fixes the following warning:

    ../src/string_search.h:113:30: warning:
    ‘search’ may be used uninitialized in this function [-Wmaybe-uninitialized]
         return (this->*strategy_)(subject, index);

Fixes: nodejs#26733
Fixes: nodejs#31532
Fixes: nodejs#31798
@bnoordhuis bnoordhuis mentioned this pull request Feb 15, 2020
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danbev commented Feb 17, 2020

Closing in favor of #31809

@danbev danbev closed this Feb 17, 2020
@danbev danbev deleted the string_search-warnings branch February 25, 2020 05:21
addaleax pushed a commit that referenced this pull request Mar 11, 2020
@bnoordhuis @addaleax
src: fix -Wmaybe-uninitialized compiler warning
d2e9177 
Turn the `strategy_` method pointer into an enum-based static dispatch.

It's both safer and more secure (no chance of method pointer corruption)
and it helps GCC see that the shift and suffix tables it's complaining
about are unused in single char search mode.

Fixes the following warning:

    ../src/string_search.h:113:30: warning:
    ‘search’ may be used uninitialized in this function [-Wmaybe-uninitialized]
         return (this->*strategy_)(subject, index);

Fixes: #26733
Refs: #31532
Refs: #31798
PR-URL: #31809
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
MylesBorins pushed a commit that referenced this pull request Mar 11, 2020
@bnoordhuis @MylesBorins
src: fix -Wmaybe-uninitialized compiler warning
fa376f4 
Turn the `strategy_` method pointer into an enum-based static dispatch.

It's both safer and more secure (no chance of method pointer corruption)
and it helps GCC see that the shift and suffix tables it's complaining
about are unused in single char search mode.

Fixes the following warning:

    ../src/string_search.h:113:30: warning:
    ‘search’ may be used uninitialized in this function [-Wmaybe-uninitialized]
         return (this->*strategy_)(subject, index);

Fixes: #26733
Refs: #31532
Refs: #31798
PR-URL: #31809
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
targos pushed a commit that referenced this pull request Apr 22, 2020
@bnoordhuis @targos
src: fix -Wmaybe-uninitialized compiler warning
a53980d 
Turn the `strategy_` method pointer into an enum-based static dispatch.

It's both safer and more secure (no chance of method pointer corruption)
and it helps GCC see that the shift and suffix tables it's complaining
about are unused in single char search mode.

Fixes the following warning:

    ../src/string_search.h:113:30: warning:
    ‘search’ may be used uninitialized in this function [-Wmaybe-uninitialized]
         return (this->*strategy_)(subject, index);

Fixes: #26733
Refs: #31532
Refs: #31798
PR-URL: #31809
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
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