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Bug 4999 - MSVC Static analysis: Incorrect alpha_value check in SDL_render.c
Summary: MSVC Static analysis: Incorrect alpha_value check in SDL_render.c
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: render (show other bugs)
Version: HG 2.1
Hardware: x86 Windows 10
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-02-21 19:53 UTC by Cameron Gutman
Modified: 2020-02-23 08:58 UTC (History)
1 user (show)

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Description Cameron Gutman 2020-02-21 19:53:57 UTC 
MSVC's static analysis found this one and it looks like a legitimate bug.

"Incorrect operator: mutual exclusion over || is always a non-zero constant.  Did you intend to use && instead?"

    /* If Palette contains alpha values, promotes to alpha format */
    if (fmt->palette) {
        for (i = 0; i < fmt->palette->ncolors; i++) {
            Uint8 alpha_value = fmt->palette->colors[i].a;
            if (alpha_value != 0 || alpha_value != SDL_ALPHA_OPAQUE) { <---- HERE
                needAlpha = SDL_TRUE;
                break;
            }
        }
    }


https://hg.libsdl.org/SDL/file/28fcb5ef7ff1/src/render/SDL_render.c#l1170
Comment 1 Sylvain 2020-02-23 08:58:44 UTC 
Thanks good catch ! palette surface were then always promoted to alpha.
https://hg.libsdl.org/SDL/rev/c66d1c7700bd

(At the same time, I spotted another issue and re-open bug 4425)