[vlc-devel] [PATCH] contrib: sidplay2: fix signed char stored as int8_t

[Rémi Denis-Courmont]

Hi,

The signedness of literal constants does not affect the occurrence of overflowing conversion. +200 cannot be represented by int8_t regardless if it's originally an unsigned int or signed int.

Le 28 janvier 2020 14:13:50 GMT+02:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>On 2020-01-11 3:47, Rémi Denis-Courmont wrote:
>> Is overflowing conversion to signed type well defined in C++? I'm
>pretty 
>> sure it's implementation-defined in C.
>
>The literal constants are signed by default. The casting from int to 
>int8_t is also signed so the values are preserved correctly. (verified 
>with gcc and llvm)
>
>> Le 10 janvier 2020 18:54:08 GMT+09:00, Steve Lhomme
><robux4 at ycbcr.xyz> a 
>> écrit :
>> 
>>     When using 0xXX notation the issue we also have to adjust the
>width.
>> 
>>     Fixes compilation with gcc 9 for Raspberry:
>> 
>>     compile:  arm-linux-gnueabihf-g++ -DHAVE_CONFIG_H
>-Icontrib/arm-linux-gnueabihf/include
>-Icontrib/arm-linux-gnueabihf/include -g -O2 -DHAVE_UNIX
>-I../../include -I../../include/sidplay -c xsid.cpp -fPIC -DPIC -o
>xsid.o
>>     xsid.cpp:101:1: error: narrowing conversion of ‘'\200'’ from
>‘char’ to ‘int8_t’ {aka ‘signed char’} [-Wnarrowing]
>>        101 | };
>>            | ^
>>     xsid.cpp:101:1: error: narrowing conversion of ‘'\224'’ from
>‘char’ to ‘int8_t’ {aka ‘signed char’} [-Wnarrowing]
>>     xsid.cpp:101:1: error: narrowing conversion of ‘'\251'’ from
>‘char’ to ‘int8_t’ {aka ‘signed char’} [-Wnarrowing]
>>     xsid.cpp:101:1: error: narrowing conversion of ‘'\274'’ from
>‘char’ to ‘int8_t’ {aka ‘signed char’} [-Wnarrowing]
>>     xsid.cpp:101:1: error: narrowing conversion of ‘'\316'’ from
>‘char’ to ‘int8_t’ {aka ‘signed char’} [-Wnarrowing]
>>     xsid.cpp:101:1: error: narrowing conversion of ‘'\341'’ from
>‘char’ to ‘int8_t’ {aka ‘signed char’} [-Wnarrowing]
>>     xsid.cpp:101:1: error: narrowing conversion of ‘'\362'’ from
>‘char’ to ‘int8_t’ {aka ‘signed char’} [-Wnarrowing]
>>     make[4]: *** [Makefile:409: xsid.lo] Error 1
>>    
>------------------------------------------------------------------------
>>       contrib/src/sidplay2/rules.mak                |  1 +
>>       contrib/src/sidplay2/sidplay2-char-cast.patch | 13
>+++++++++++++
>>       2 files changed, 14 insertions(+)
>>       create mode 100644
>contrib/src/sidplay2/sidplay2-char-cast.patch
>> 
>>     diff --git a/contrib/src/sidplay2/rules.mak
>b/contrib/src/sidplay2/rules.mak
>>     index 84c35ccfee7..de77935774a 100644
>>     --- a/contrib/src/sidplay2/rules.mak
>>     +++ b/contrib/src/sidplay2/rules.mak
>>     @@ -25,6 +25,7 @@ sidplay-libs:
>sidplay-libs-$(SID_VERSION).tar.gz .sum-sidplay2
>>       	$(APPLY) $(SRC)/sidplay2/sidplay2-string.patch
>>       	$(APPLY) $(SRC)/sidplay2/sidplay-fix-ln-s.patch
>>       	$(APPLY) $(SRC)/sidplay2/sidplay2-resid-dependency.patch
>>     +	$(APPLY) $(SRC)/sidplay2/sidplay2-char-cast.patch
>>       	$(MOVE)
>>       
>>       .sidplay2: sidplay-libs
>>     diff --git a/contrib/src/sidplay2/sidplay2-char-cast.patch
>b/contrib/src/sidplay2/sidplay2-char-cast.patch
>>     new file mode 100644
>>     index 00000000000..14eda139606
>>     --- /dev/null
>>     +++ b/contrib/src/sidplay2/sidplay2-char-cast.patch
>>     @@ -0,0 +1,13 @@
>>     +--- sidplay-libs/libsidplay/src/xsid/xsid.cpp.char	2004-06-14
>22:08:02.000000000 +0200
>>     ++++ sidplay-libs/libsidplay/src/xsid/xsid.cpp	2020-01-10
>08:41:49.454974200 +0100
>>     +@@ -96,8 +96,8 @@ const int8_t XSID::sampleConvertTable[16
>>     + */
>>     + const int8_t XSID::sampleConvertTable[16] =
>>     + {
>>     +-    '\x80', '\x94', '\xa9', '\xbc', '\xce', '\xe1', '\xf2',
>'\x03',
>>     +-    '\x1b', '\x2a', '\x3b', '\x49', '\x58', '\x66', '\x73',
>'\x7f'
>>     ++    (int8_t)0x80, (int8_t)0x94, (int8_t)0xa9, (int8_t)0xbc,
>(int8_t)0xce, (int8_t)0xe1, (int8_t)0xf2, (int8_t)0x03,
>>     ++    (int8_t)0x1b, (int8_t)0x2a, (int8_t)0x3b, (int8_t)0x49,
>(int8_t)0x58, (int8_t)0x66, (int8_t)0x73, (int8_t)0x7f
>>     + };
>>     +
>>     + const char *XSID::credit =
>> 
>> 
>> -- 
>> Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez
>excuser 
>> ma brièveté.
>> 
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-- 
Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez excuser ma brièveté.
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