Here are a few simplest and most interesting bugs found by the PVS-Studio analyzer in the RT-Thread project.

PVS-Studio is a tool for detecting errors and potential vulnerabilities in the source code of applications written in С, C++, and C#. The analyzer supports Windows and Linux (in addition, a macOS version will be released soon). https://www.viva64.com/en/pvs-studio/

RT-Thread is an open source IoT operating system from China, which has strong scalability: from a tiny kernel running on a tiny core, for example ARM Cortex-M0, or Cortex-M3/4/7, to a rich feature system running on MIPS32, ARM Cortex-A8, ARM Cortex-A9 DualCore etc. https://github.com/RT-Thread/rt-thread

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PVS-Studio diagnostic messages:

V560 CWE-571 A part of conditional expression is always true: 0xFFFF0000. peci.c 372
V560 CWE-571 A part of conditional expression is always true: 0x0000FFFF. peci.c 373

#define PECI_M0D0C_HITHR_M      0xFFFF0000  // High Threshold
#define PECI_M0D0C_LOTHR_M      0x0000FFFF  // Low Threshold

void
PECIDomainConfigGet(....)
{
  unsigned long ulTemp;
  ....
  ulTemp = HWREG(ulBase + PECI_O_M0D0C + (ulDomain * 4));
  *pulHigh =
    ((ulTemp && PECI_M0D0C_HITHR_M) >> PECI_M0D0C_HITHR_S);
  *pulLow =
    ((ulTemp && PECI_M0D0C_LOTHR_M) >> PECI_M0D0C_LOTHR_S);
}

The & operator should be used instead of &&.
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PVS-Studio diagnostic message:

V767 Suspicious access to element of 'w' array by a constant index inside a loop. fsl_dcp.c 946

typedef union _dcp_hash_block
{
    uint32_t w[DCP_HASH_BLOCK_SIZE / 4];
    uint8_t b[DCP_HASH_BLOCK_SIZE];
} dcp_hash_block_t;

typedef struct _dcp_hash_ctx_internal
{
  dcp_hash_block_t blk;
  ....
} dcp_hash_ctx_internal_t;

status_t DCP_HASH_Init(DCP_Type *base, dcp_handle_t *handle,
                       dcp_hash_ctx_t *ctx, dcp_hash_algo_t algo)
{
  ....
  dcp_hash_ctx_internal_t *ctxInternal;
  ....
  for (i = 0; i < sizeof(ctxInternal->blk.w) /
                            sizeof(ctxInternal->blk.w[0]); i++)
  {
     ctxInternal->blk.w[0] = 0u;
  }
  ....
}

The value 0 is written into one and the same array element. The major part of the array will remain uninitialized. The correct version looks like this:
ctxInternal->blk.w[i] = 0u;
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PVS-Studio diagnostic messages:

V602 CWE-480 Consider inspecting the '(1U < 1)' expression. '<' possibly should be replaced with '<<'. fsl_aipstz.h 69
V602 CWE-480 Consider inspecting the '(1U < 2)' expression. '<' possibly should be replaced with '<<'. fsl_aipstz.h 70
V602 CWE-480 Consider inspecting the '(1U < 2)' expression. '<' possibly should be replaced with '<<'. fsl_aipstz.h 71

typedef enum _aipstz_peripheral_access_control {
  kAIPSTZ_PeripheralAllowUntrustedMaster = 1U,
  kAIPSTZ_PeripheralWriteProtected = (1U < 1),
  kAIPSTZ_PeripheralRequireSupervisor = (1U < 2),
  kAIPSTZ_PeripheralAllowBufferedWrite = (1U < 2)
} aipstz_peripheral_access_control_t;

The << operator should be used instead of <. The constants would then equal to different powers of 2.
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