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https://issues.apache.org/jira/browse/STDCXX-163?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Sebor updated STDCXX-163:
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Severity: Inefficiency
Affects Version/s: 4.1.2
4.1.4
4.2.0
Fix Version/s: 5.0
This affects all released versions and can't be fixed w/o breaking binary
compatibility.
Scheduled for 5.0.
> ios_base data member layout wastes 2 bytes
> ------------------------------------------
>
> Key: STDCXX-163
> URL: https://issues.apache.org/jira/browse/STDCXX-163
> Project: C++ Standard Library
> Issue Type: Improvement
> Components: 27. Input/Output
> Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0
> Environment: all
> Reporter: Martin Sebor
> Priority: Minor
> Fix For: 5.0
>
>
> The latest HP aCC beta points out a space inefficiency in the definition of
> the ios_base class. The next time we break binary compatibility we should
> rearrange the data mebers to avoid the wasted space.
> aCC -c -D_RWSTD_USE_CONFIG -I/build/sebor/aCC-6.07-8s/include
> -I/build/sebor/dev/stdlib/include -AA +O2 +w +wlint +W392 +W655 +W684
> +W818 +W819 +W849 +W2193 +W2236 +W2261 +W2340 +W2401 +W2487 +W4255
> /build/sebor/dev/stdlib/src/iostream.cpp
> "/build/sebor/dev/stdlib/include/rw/_iosbase.h", line 357: remark #4227-D:
> padding struct with 2 bytes to align member "_C_usr"
> _C_usr_data *_C_usr; // user data (iword, pword, callbacks)
> ^
> $ cat -n /build/sebor/dev/stdlib/include/rw/_iosbase.h | head -n 360 | tail
> -n 33
> 328 void *_C_rdbuf; // pointer to the associated
> stream buffer
> 329 _RWSTD_STREAMSIZE _C_prec; // current precision
> 330 _RWSTD_STREAMSIZE _C_wide; // current width
> 331 unsigned _C_fmtfl; // formatting flags
> 332 unsigned char _C_state; // stream state
> 333 unsigned char _C_except; // active exceptions
> 334
> 335 static bool _C_sync_with_stdio;
> 336
> 337 private:
> 338
> 339 ios_base (const ios_base&); // not defined
> 340 ios_base& operator= (const ios_base&); // not defined
> 341
> 342 #if __EDG_VERSION__ < 245
> 343
> 344 // working around an EDG eccp 2.3x bug (also derivatives,
> 345 // such as MIPSpro, see PR #28631)
> 346 public:
> 347 struct _C_usr_data;
> 348
> 349 #else
> 350
> 351 protected:
> 352 struct _C_usr_data;
> 353
> 354 #endif // EDG < 2.45
> 355
> 356 protected:
> 357 _C_usr_data *_C_usr; // user data (iword, pword, callbacks)
> 358 locale _C_loc; // locale associated with stream
> 359
> 360 friend struct _RWSTD_EXPORT Init;
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