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Suppress (GitHub CI/wayland) compiler warning 

[ 15%] Building CXX object src/CMakeFiles/fltk.dir/Fl_Text_Display.cxx.o
.../fltk/src/Fl_Text_Display.cxx: In constructor ‘Fl_Text_Display::Fl_Text_Display(int, int, int, int, const char*)’:
.../fltk/src/Fl_Text_Display.cxx:122:57: warning: ‘void* __builtin_memset(void*, int, long unsigned int)’ writing between 4 and 8589934584 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
  122 |     for (int i=1; i<mNVisibleLines; i++) mLineStarts[i] = -1;
      |                                          ~~~~~~~~~~~~~~~^~~~
.../fltk/src/Fl_Text_Display.cxx:120:39: note: at offset 4 into destination object of size 4 allocated by ‘operator new []’
  120 |   mLineStarts = new int[mNVisibleLines];
      |                                       ^

This warning is IMHO obsolete because the code in question should not
be executed at all (mNVisibleLines == 1). However, the compiler seems
to substitute this with '__builtin_memset(...)' and analyzes "correctly"
that memory at offset 4 would be overwritten but not that the written
size would be 0.

The "fix" uses a compiler macro and #if to clarify that this code must
not be executed and should not be compiled (see comment why this code
exists).
This commit is contained in:
Albrecht Schlosser 2022-12-09 18:33:14 +01:00
parent 59be6a7ef9
commit ceb268fd34
1 changed files with 6 additions and 2 deletions
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8
src/Fl_Text_Display.cxx
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@ -97,6 +97,8 @@ static int scroll_x = 0;
Fl_Text_Display::Fl_Text_Display(int X, int Y, int W, int H, const char* l)
: Fl_Group(X, Y, W, H, l) {
#define VISIBLE_LINES_INIT 1 // allow compiler to remove unused code (PR #582)
// Member initialization: same order as declared in .H file
// Any Fl_Text_Display methods should only be called /after/ all
// members initialized; avoids methods referencing uninitialized values.
@ -109,7 +111,7 @@ Fl_Text_Display::Fl_Text_Display(int X, int Y, int W, int H, const char* l)
mCursorToHint = NO_HINT;
mCursorStyle = NORMAL_CURSOR;
mCursorPreferredXPos = -1;
mNVisibleLines = 1;
mNVisibleLines = VISIBLE_LINES_INIT;
mNBufferLines = 0;
mBuffer = NULL;
mStyleBuffer = NULL;
@ -118,9 +120,11 @@ Fl_Text_Display::Fl_Text_Display(int X, int Y, int W, int H, const char* l)
mContinuousWrap = 0;
mWrapMarginPix = 0;
mLineStarts = new int[mNVisibleLines];
{ // This code unused unless mNVisibleLines is ever initialized >1
#if VISIBLE_LINES_INIT > 1
{ // Note: this code is unused unless mNVisibleLines is ever initialized > 1
for (int i=1; i<mNVisibleLines; i++) mLineStarts[i] = -1;
}
#endif
mLineStarts[0] = 0;
mTopLineNum = 1;
mAbsTopLineNum = 1;