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#81 Fix casting pointer to different size integer#23

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ooxi merged 1 commit intogerbv:mainfrom
ooxi:patch/81-fix-casting-pointer-to-different-size-integer
Sep 16, 2021
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#81 Fix casting pointer to different size integer#23
ooxi merged 1 commit intogerbv:mainfrom
ooxi:patch/81-fix-casting-pointer-to-different-size-integer

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@ooxi
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@ooxi ooxi commented Sep 16, 2021

src/scheme.c has the problem of casting pointers to int of different sizes. This problem becomes apparent in 64-bit compilers.

But changed uintptr_t to size_t as discussed in Pull Request #20 by @efa

See SourceForge patch #81 by Hiroshi Yoshikawa

--- a/src/scheme.c	2020-10-22 07:12:44.000000000 +0900
+++ b/src/scheme.c	2021-08-03 22:15:56.721406100 +0900
@@ -568,7 +568,7 @@ static int alloc_cellseg(scheme *sc, int
      char *cp;
      long i;
      int k;
-     unsigned int adj=ADJ;
+     uintptr_t adj=ADJ;
 
      if(adj<sizeof(struct cell)) {
        adj=sizeof(struct cell);
@@ -583,8 +583,8 @@ static int alloc_cellseg(scheme *sc, int
 	  i = ++sc->last_cell_seg ;
 	  sc->alloc_seg[i] = cp;
 	  /* adjust in TYPE_BITS-bit boundary */
-	  if((unsigned long)cp%adj!=0) {
-	    cp=(char*)(adj*((unsigned long)cp/adj+1));
+	  if((uintptr_t)cp%adj!=0) {
+	    cp=(char*)(adj*((uintptr_t)cp/adj+1));
 	  }
         /* insert new segment in address order */
 	  newp=(pointer)cp;

@efa @ooxi
SourceForge gerbv#81 Fix casting pointer to different size integer
26c90bd 
But changed 'uintptr_t' to 'size_t' as opening a .gvp file on Windows always crash

I re-tested also on Linux

https://sourceforge.net/p/gerbv/patches/81/
@ooxi ooxi marked this pull request as ready for review September 16, 2021 08:51
@ooxi ooxi merged commit e4b344e into gerbv:main Sep 16, 2021
@ooxi ooxi deleted the patch/81-fix-casting-pointer-to-different-size-integer branch September 16, 2021 08:51
@ooxi ooxi mentioned this pull request Sep 16, 2021
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@eyal0
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eyal0 commented Sep 17, 2021

If you are worried about a cast from one type to another type of a different size, the best protection is to have the compiler enforce it.

static_assert(sizeof(uintptr_t) == sizeof(cp))

This solution will catch bugs on all architectures, even ones that we haven't encountered yet. It's nice when we have have the computer find our bugs for us automatically.

@efa
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efa commented Sep 17, 2021

to me seems a good idea. Please add a PR for this

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@ooxi @eyal0 @efa